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12 Cards in this Set

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A 25-year-old man visits the emergency department with a complaint of painful urination. Symptoms began 3 days ago. He also is having generalized pain and stiffness in his joints. On examination, he has a temperature of 38.7°C (101.8°F), nonexudative pharyngitis, and a maculopapular rash on the torso and palms of his hands. There is decreased range of motion in his extremities. He has a purulent urethral discharge. Which of the following is indicated to treat this patient’s condition?

Answer Choices Correct AnswerCorrect answer Your AnswerYour answer
A. Cefixime
B. Ciprofloxacin
C. Erythromycin
D. Penicillin G
E. Spectinomycin
Option A (Cefixime) is correct. Cefixime is the first-line drug of choice because it is effective against gonorrhea and Chlamydia infections, can be taken orally, is inexpensive, and requires only single-dose treatment. If a patient is penicillin allergic, he or she may have cross-sensitivity to cephalosporins.

Option B (Ciprofloxacin) is incorrect. Ciprofloxacin is not recommended. Neisseria gonorrhoeae has developed high-level resistance to quinolones in many geographic areas.

Option C (Erythromycin) is incorrect. Erythromycin is not recommended as the treatment for disseminated gonococcal infection. The antibiotic regimen should have efficacy against N. gonorrhoeae and Chlamydia.

Option D (Penicillin G) is incorrect. Broad resistance among N. gonorrhoeae organisms to penicillin has made this drug largely ineffective in treatment of these infections.

Option E (Spectinomycin) is incorrect. Spectinomycin is a second-line choice for treatment of disseminated gonococcal infection owing to poor efficacy in pharyngitis, but it is indicated for patients with β-lactam intolerance. The patient may be cross-sensitive to cephalosporins.

High-yield Hit 1
General treatment guidelines for lower genital tract gonorrhea infection include: (1) treatment with appropriate antibiotics (e.g., cefixime 400 mg orally in a single dose or ceftriaxone 125 mg IM in a single dose); (2) simultaneous treatment for Chlamydia (i.e., 1 g of azithromycin orally in a single dose) because 20% to 40% of gonococcal cervical infections also have Chlamydia; (3) treatment of all sexual contacts within the past 60 days prior to diagnosis; (4) abstinence from sexual activity for 7 days after the start of antibiotic therapy; (5) testing for other STIs, including Chlamydia, syphilis, hepatitis B, HIV. Test of cure is not necessary, however, rescreening in 3 to 4 months to check for reinfection may be helpful.

Taken from Essentials of Obstetrics & Gynecology 4E by Hacker et a
A 72-year-old man presents to an urgent-care clinic for evaluation and treatment of a sore on his left leg. He says that the sore first appeared several months ago but has recently increased in size, becoming painful within the last 2 weeks. The sore has also begun to drain yellowish fluid, over the past 3 weeks. He says that he has another sore on his right leg that is similar, but smaller, which has been present for about 4 weeks. His past medical history is significant only for hypertension, for which he takes hydochlorothiazide. On physical examination, you note a well-nourished, medium-build man who appears his stated age. Head and neck, chest, and abdominal examinations are normal. Cardiac sounds are normal. Lower extremities are noted to have varicose veins in the popliteal fossae and over both calves. Both legs are slightly edematous and purplish-red distally to about 5 cm distal to the knees. The skin over this area is mottled in appearance with purplish-brown discoloration in the skin creases about the ankles. A wound on the left, medial malleolus is shown in the figure and there is a similar, smaller, 1 x 2cm wound on the right medial malleolus. Which of the following would be appropriate for first-line treatment of the underlying condition?
Rmp110f1

Answer Choices Correct AnswerCorrect answer Your AnswerYour answer
A. Arterial bypass grafting of the affected area
B. Sclerotherapy of the varicose veins
C. Use of a broad-spectrum antibiotic
D. Use of oral hyperglycemic agents
E. Use of support stockings when upright
CHRONIC VENOUS DISEASE
Varicose veins are caused by incompetent valves in the saphenous veins and may result from any condition that results in an increase in intra-abdominal pressure (e.g., pregnancy, ascites) or interferes with venous drainage from the lower extremities (e.g., intra-abdominal tumors, pelvic vein thrombosis). Varicosities may cause local discomfort, may be complicated by thrombosis (thrombophlebitis), and cause chronic edema. Treatment is initially conservative with compression stockings; sclerotherapy and surgical venous stripping are reserved for refractory cases. Chronic venous insufficiency may follow deep venous thrombophlebitis and results in chronic edema. Treatment also involves the use of support stockings and leg elevation. Leg ulcers commonly develop in the setting of venous stasis and require antibiotics and compressive bandages for optimal healing.
Edema caused by chronic venous disease or elevated venous pressure (e.g., right-sided heart failure, cirrhosis) must be distinguished from that caused by ineffective lymphatic drainage (lymphedema). Venous disease produces pitting edema and an increased superficial venous pattern, involves the foot but not the toes, and is associated with relatively normal skin. Lymphedema is nonpitting, does not result in superficial venous prominence, involves the foot and the toes, and is associated with thickened skin. Lymphedema may be congenital (e.g., Milroy's disease), postinfectious, obstructive as a result of pelvic neoplasms, or iatrogenic after surgical removal of lymph nodes. Compression stocking use is the mainstay of therapy.

From Cecil Essentials of Medicine 6E by Andreoli et al
A 32-year-old woman returns to her community health clinic complaining of tingling in her hands and feet. The symptoms began 3 days ago. She has no other complaints. Four weeks ago, she had a positive purified protein derivative (PPD) skin test and a normal chest radiograph. She was started on prophylactic isoniazid. She is a third grade teacher and an immigrant from the Philippines. She has been in the United States for 5 years. Which of the following is the best explanation for her symptoms?

Answer Choices Correct AnswerCorrect answer Your AnswerYour answer
A. Conversion reaction
B. Dietary thiamine deficiency
C. Isoniazid hypersensitivity reaction
D. Pernicious anemia
E. Pyridoxine deficiency
Option E (Pyridoxine deficiency) is correct. Isoniazid is known to inhibit the formation of the biologically active form of pyridoxine or vitamin B6. Thus, when administering isoniazid, many physicians also have their patients take a vitamin B6 supplement to prevent the peripheral neuritis that can otherwise result in about 2% of patients.

Option A (Conversion reaction) is incorrect. With no other historical background of psychiatric disorders or social stressors, this seems very unlikely. Be aware, though, that there have been reports of patients having psychotic episodes with this drug.

Option B (Dietary thiamine deficiency) is incorrect. Thiamine deficiency causes distal neuropathy, but there is no reason to suspect thiamine deficiency in this patient. Isoniazid is known to inhibit the formation of the biologically active form of pyridoxine or vitamin B6.

Option C (Isoniazid hypersensitivity reaction) is incorrect. This is occurring too much later and too atypically for a type I reaction. Recall that type I hypersensitivity reactions result from the release of inflammatory mediators from mast cells and basophils, so they will manifest with symptoms such as rhinorrhea, shortness of breath, and swelling, as with an anaphylactic reaction.

Option D (Pernicious anemia) is incorrect. Cobalamin deficiency can cause peripheral neuropathy, but this is a less likely cause than isoniazid inhibition of the formation of the biologically active form of pyridoxine or vitamin B6.

High-yield Hit 1
Isoniazid
Isoniazid inhibits mycobacteria and is given with pyridoxine to prevent neurologic side effects
Isoniazid is isonicotinic acid hydrazide, a compound that inhibits mycobacteria, but does not affect other species of bacteria or humans to any great extent. Its bacteriocidal activity results from inhibition of mycolic acid synthesis, which also accounts for its specificity. It is well absorbed after oral administration, and a single daily dose is usually prescribed except in more difficult cases such as meningitis or miliary tuberculosis. The main toxic effects in humans are neurologic complications, which can be prevented by the concurrent administration of pyridoxine, and hepatitis.
A 33-year-old woman with human immunodeficiency virus (HIV) presents to the physician for her regular follow-up care. She was diagnosed 3 years ago and is taking highly active antiretroviral therapy. Her last CD4 cell count was 475 cells/μL and she is currently asymptomatic. She states that she recently found her old medical records and discovered that she was never immunized against any diseases. What vaccine is contraindicated in this patient?

Answer Choices Correct AnswerCorrect answer Your AnswerYour answer
A. Haemophilus influenzae type b (HiB) conjugate vaccine
B. Hepatitis B vaccine
C. Measles, mumps, rubella (MMR) combined vaccine
D. Pneumococcal vaccine
E. Varicella vaccine
Option E (Varicella vaccine) is correct. Vaccination schedules are unlikely to be examined on the U.S. Medical Licensing Examination. However, exceptions to vaccination and special circumstances are likely topics. In HIV-positive individuals, live vaccines are generally contraindicated. This includes varicella, bacille Calmette-Guérin, vaccinia, oral typhoid, and yellow fever.

Option A (Haemophilus influenzae type b [HiB] conjugate vaccine) is incorrect. This vaccine is not recommended, because HiB is not common in HIV patients. Most H. influenzae infections are nontypeable and thus not prevented by vaccine.

Option B (Hepatitis B vaccine) is incorrect. Chronic hepatitis is more likely to develop in HIV patients following hepatitis B infection compared to immunocompetent individuals. Thus, this vaccine is recommended.

Option C (Measles, mumps, rubella [MMR] combined vaccine) is incorrect. A live vaccine, MMR it is not contraindicated in HIV patients so long as they are severely symptomatic. The reason for this is because the HIV patients are highly susceptible to measles. Contraindication in AIDS patients is because of a report of measles pneumonitis following vaccination.

Option D (Pneumococcal vaccine) is incorrect. Although it appears that HIV patients respond suboptimally to this vaccine, their risk of developing pneumococcal disease is very high and thus, vaccination is strongly recommended as soon as the CD4 count is more than 200 following HIV diagnosis.

High-yield Hit 1
Table 5-18. Recommendations for Persons with Medical Conditions Requiring Special Vaccination Considerations
Condition Td MMR Varicella HBV HAV Pneumovaxa Influenzab HbCV Meningococcal IPV Other live vaccinesc Other Killed Vaccinesd
HIV infection Rou Rou/Contre Contrf Roug Rou Rec Rec Cons Rou Rou Contr Rou
Severe immunocompromiseh Rou Contr Contrf Roug Rou Rec Rec Roui Rou Rou Contr Rou
Renal failure Rou Rou Rou Recg Rou Rec Rec Rou Rou Rou Rou Rou
Diabetes Rou Rou Rou Rou Rou Rec Rec Rou Rou Rou Rou Rou
Chronic liver disease Rou Rou Rou Rou Rec Rec Rec Rou Rou Rou Rou Rou
Cardiac disease Rou Rou Rou Rou Rou Rec Rec Rou Rou Rou Rou Rou
Pulmonary disease Rou Rou Rou Rou Rou Rec Rec Rou Rou Rou Rou Rou
Alcoholism Rou Rou Rou Rou Rou Rec Rec Rou Rou Rou Rou Rou
Functional/anatomic asplenia Rou Rou Rou Rou Rou Recj Rec Recj Recj Rou Rou Rou
Terminal complement deficiency Rou Rou Rou Rou Rou Rou Rou Rou Rec Rou Rou
Clotting factor disorders Rou Rou Rou Rec Rec Rou Rou Rou Rou Rou Rou Rou

From Ferri's Clinical Advisor 2006 by Ferri
A 45-year-old man is brought into the emergency department with a 2-day history of elevated mood, pressured speech, and decreased need for sleep. His symptoms began suddenly and have progressively worsened. He has no previous medical history and does not take any regular or illicit drugs. He is admitted to the psychiatric service. The following day, he develops a decreased level of consciousness, fever and dysphasia. His gait is ataxic and he has accentuated deep tendon reflexes. What is the most likely diagnosis?

Answer Choices Correct AnswerCorrect answer Your AnswerYour answer
A. Herpes simplex virus (HSV) encephalitis
B. Meningococcal meningitis
C. Mumps encephalitis
D. Pseudotumor cerebri
E. West Nile virus encephalitis
Option A (Herpes simplex virus [HSV] encephalitis) is correct. This patient most likely has HSV encephalitis. The clue to most presentations of encephalitis is fever and mental status changes. In HSV encephalitis, there is a predilection for the temporal lobes, which can produce frankly psychotic states. A bipolar-type picture is present in this case. The sudden deterioration, combined with fever and seizures, gives rise to the presumptive diagnosis. Definitive diagnosis is with polymerase chain reaction analysis of cerebrospinal fluid for HSV DNA.

Option B (Meningococcal meningitis) is incorrect. Meningococcal meningitis often presents with a petechial rash, along with headache, fever, neck stiffness, and photophobia. Meningococcus is the second most common cause of meningitis in adults, behind pneumococcus.

Option C (Mumps encephalitis) is incorrect. Mumps encephalitis should be suspected in a patient who is unvaccinated and presents with parotitis and mental status changes.

Option D (Pseudotumor cerebri) is incorrect. Pseudotumor cerebri, also known as benign intracranial hypertension, is often manifest in young females. It presents with early morning headaches and visual disturbances.

Option E (West Nile virus encephalitis) is incorrect. West Nile virus encephalitis should be suspected if there is a maculopapular rash, mental status changes, and flaccid paralysis in an area where West Nile virus is present.

High-yield Hit 1
Encephalitis

1. Cause: Usually viral; history may include a recent insect, tick, or animal bite
2. Signs and symptoms
1. May manifest as fevers, headaches, impaired consciousness, confusion
2. Presence of seizures and/or focal deficits distinguishes encephalitis from meningitis
3. Types
1. Herpes encephalitis
* (1) Associated with herpes simplex virus 1 (oral herpes) infection.
* (2) Can cause aphasia, memory impairment, and behavioral changes due to damage to the frontal and temporal lobes.
* (3) Mortality rate is as high as 70% without treatment. With acyclovir therapy, the rate decreases to 20%.
2. Insect- or tick-borne encephalitis
* (1) California group (LaCrosse)
o (a) Viral prodrome can progress to fever, somnolence, obtundation, and seizures.
o (b) Most severe in children 4 to 11 years of age.
* (2) St. Louis encephalitis
o (a) Viral prodrome progresses to confusion, disorientation, stupor, tremors, and convulsions.
o (b) Severity increases with age.
* (3) West Nile virus infection
o (a) Viral prodrome can progress to a maculopapular rash, diarrhea, and encephalitic symptoms.
o (b) Distinguishing feature: May cause axonal neuropathy, resulting in a presentation similar to Guillain-Barré syndrome.
* (4) Colorado tick fever: Viral prodrome progresses to a fever that recurs every 2 to 3 days along with other symptoms of encephalitis and aseptic meningitis.

Poliomyelitis: Weakness due to infection of motor neurons in the brain and spinal cord

From Rapid Review USMLE Step 2 by Lawlor
You are seeing a 67-year-old retired man with diabetes mellitus and hypertension in early November. He is new to your city and is looking to establish care with you as the primary physician. You review his medical history, and he states he has never received any vaccinations other than those administered when he was a child. Which of the following vaccinations are recommended?

Answer Choices Correct AnswerCorrect answer Your AnswerYour answer
A. Diphtheria tetanus and Hepatitis A
B. Diphtheria tetanus, influenza, and pertussis
C. Diphtheria tetanus, influenza, and pneumococcus
D. Diphtheria tetanus, pneumococcus, and Hepatits A
E. Influenza, varicella, and pertussis
Option C (Diphtheria tetanus, influenza, and pneumococcus) is correct. Pneumococcus and influenza virus vaccines are recommended vaccinations for elderly patients and patients with comorbidities. The diphtheria and tetanus vaccine is recommended every 10 years.

Option A (Diphtheria tetanus and Hepatitis A) is incorrect. Pneumococcus and influenza virus vaccines are recommended vaccinations for elderly patients and patients with comorbidities. The diphtheria and tetanus vaccine is recommended every 10 years.

Option B (Diphtheria tetanus, influenza, and pertussis) is incorrect. Pneumococcus and influenza virus vaccines are recommended vaccinations for elderly patients and patients with comorbidities. The diphtheria and tetanus vaccine is recommended every 10 years.

Option D (Diphtheria tetanus, pneumococcus, and Hepatits A) is incorrect. Pneumococcus and influenza virus vaccines are recommended vaccinations for elderly patients and patients with comorbidities. The diphtheria and tetanus vaccine is recommended every 10 years.

Option E (Influenza, varicella, and pertussis) is incorrect. Pneumococcus and influenza virus vaccines are recommended vaccinations for elderly patients and patients with comorbidities. The diphtheria and tetanus vaccine is recommended every 10 years.
A 40-year-old man presents to the emergency room, because of a painful lesion on his right lower leg. He states that he awoke this morning and noticed that it was extremely painful and swollen. His previous medical history is notable for recurrent tinea pedis. He does not currently take any regular medications and has no known allergies. His vital signs are blood pressure, 125/80 mm Hg; pulse, 82 beats/min; temperature, 38.5°C (101.3°F); and respirations, 14 breaths/min. There is a 5- x 4-cm erythematous, edematous patch with an indistinct margin over the lateral lower leg. Laboratory investigation reveals leukocytosis. What is the most likely diagnosis?

Answer Choices Correct AnswerCorrect answer Your AnswerYour answer
A. Angioedema
B. Cellulitis
C. Erysipeloid
D. Furuncle
E. Impetigo
Option B (Cellulitis) is correct. This patient is experiencing a case of cellulitis, an infection of the lower dermis and subcutaneous fat. The lesion is unilateral and flat (hence the term patch) that is poorly demarcated because of the depth of infection. Group A streptococci, Staphylococcus aureus, and Haemophilus influenzae are all common causes. Fever, lymphadenopathy, and a leukocytosis may be observed. The diagnosis is usually clinical.

Option A (Angioedema) is incorrect. Angioedema is a deep swelling of the skin that is often accompanied by swelling of the tongue, lips, and eyes. It can be hereditary or acquired.

Option C (Erysipeloid) is incorrect. Erysipeloid is like erysipelas (hence the -oid) but is an occupational disease of the hands in fish and meat workers. It is caused by Erysipelothrix rhusiopathiae and causes well-demarcated purple-red lesions of the hands (classically in the interdigital webs).

Option D (Furuncle) is incorrect. A furuncle is also known as a boil and is formed from a folliculitis. It presents as a red, hot, and painful nodule (i.e., palpable deep lesion less than 1 cm in diameter) and is most often caused by S. aureus.

Option E (Impetigo) is incorrect. Impetigo is a bacterial infection that occurs most commonly in children on the face, arms, legs, and buttocks. Initially there are vesicles that progress to the classic honey-crusted lesions, which are surrounded by erythema.

High-yield Hit 1
Cellulitis (PTG)
BASIC INFORMATION
DEFINITION
Cellulitis is a superficial inflammatory condition of the skin. It is characterized by erythema, warmth, and tenderness of the area involved.

From Ferri's Clinical Advisor 2006 by Ferri
High-yield Hit 2
EPIDEMIOLOGY & DEMOGRAPHICS

* Occurs most frequently in diabetics, immunocompromised hosts, and patients with venous and lymphatic compromise.
* Frequently found near skin breaks (trauma, surgical wounds, ulcerations, tinea infections). Edema, animal or human bites, subadjacent osteomyelitis, and bacteremia are potential sources of cellulites

PHYSICAL FINDINGS & CLINICAL PRESENTATION
Variable with the causative organism

* Erysipelas: superficial-spreading, warm, erythematous lesion distinguished by its indurated and elevated margin; lymphatic involvement and vesicle formation are common.
* Staphylococcal cellulitis: area involved is erythematous, hot, and swollen; differentiated from erysipelas by nonelevated, poorly demarcated margin; local tenderness and regional adenopathy are common; up to 85% of cases occur on the legs and feet.
* H. influenzae cellulitis: area involved is a blue-red/purple-red color; occurs mainly in children; generally involves the face in children and the neck or upper chest in adults.
* Vibrio vulnificus: larger hemorrhagic bullae, cellulitis, lymphadenitis, myositis; often found in critically ill patients in septic shock.

ETIOLOGY

* Group A β-hemolytic streptococci (may follow a streptococcal infection of the upper respiratory tract)
* Staphylococcal cellulitis
* H. influenzae
* Vibrio vulnificus: higher incidence in patients with liver disease (75%) and in immunocompromised hosts (corticosteroid use, diabetes mellitus, leukemia, renal failure)
* Erysipelothrix rhusiopathiae: common in people handling poultry, fish, or meat
* Aeromonas hydrophila: generally occurring in contaminated open wound in fresh water
* Fungi (Cryptococcus neoformans): immunocompromised granulopenic patients
* Gram-negative rods (Serratia, Enterobacter, Proteus, Pseudomonas): immunocompromised or granulopenic patients


From Ferri's Clinical Advisor 2006 by Ferri
High-yield Hit 3
Table 100-3. Processes That May Resemble Cellulitis
Process Diagnosis
Thrombophlebitis Tender cord, no lymphangitis, ultrasound
Arthitis Pain on passive joint movement, joint effusion, joint aspiration
Ruptured Baker's cyst History of arthritis, joint effusion, arthrogram, MRI
Brown recluse spider bite Exposure history
Fasciitis MRI, surgical exploration
Myositis Muscle tenderness, less prominent skin involvement, MRI, surgical exploration

From Cecil Essentials of Medicine 6E by Andreoli et
A 22-year-old female presents to her physician with a rash that has lasted 5 days. She says that the rash started on her hands and is now spreading to her axillae. She denies any fever or chills and does not have a history of allergies. Vital signs are normal. On examination there are small linear lesions in the web spaces of her hands. There are also small papules spreading up her arms. The rash is blanching and pruritic. What is the most appropriate treatment for her condition?

Answer Choices Correct AnswerCorrect answer Your AnswerYour answer
A. Diphenhydramine
B. Doxycycline
C. Fluconazole
D. Permethrin
E. Quinine
Option D (Permethrin) is correct. Permethrin cream that is put on topically and left on for 12 hours prior to showering is the treatment of choice for scabies. Scabies can be transmitted sexually or among people who share clothes or living arrangements. Patients must also wash all clothes, bedding, and the like in very hot water.

Option A (Diphenhydramine) is incorrect. Diphenhydramine is used to treat urticaria and other allergic reactions. The patient can use this to decrease the symptoms, but it will not cure the infection.

Option B (Doxycycline) is incorrect. Doxycycline does not play a role in the treatment of scabies. It can be used as part of a regimen to cover methicillin-resistant Staphylococcus aureus skin infection.

Option C (Fluconazole) is incorrect. Fluconazole is used to treat topical fungal infections such as tinea corporis.

Option E (Quinine) is incorrect. Quinine is used to treat malaria and restless leg syndrome.

High-yield Hit 1
Scabies

1. Linear burrows and extreme pruritus. These burrows are more often seen in the skin creases, but face and scalp can be involved in infants
2. All family members and bed linens need to be treated
3. Treatment: 5% permethrin cream for 12 hours. Itching can persist for 2 weeks


From Rapid Review USMLE Step 2 by Lawlor
A 51-year-old woman presents to the emergency department in the state of Connecticut. She states that she went hiking in the woods for an hour and discovered a tick on her lower leg at the end of the hike. She promptly removed it using tweezers and slow steady force. She does not have any present symptoms. Physical examination reveals a solitary tick bite on her lower leg. She is concerned about the possibility of Lyme disease. What is the most appropriate management of this patient?

Answer Choices Correct AnswerCorrect answer Your AnswerYour answer
A. Amoxicillin
B. Ceftriaxone
C. Enzyme-linked immunosorbent assay for Borrelia burgdorferi
D. Observation
E. Trimethoprim-sulfamethoxazole
Option D (Observation) is correct. The subject of prevention of Lyme disease is somewhat controversial. At present, if the tick is removed within 48 hours or does not appear to be engorged, observation is the preferred management. Lyme disease is not difficult to treat, and if observation can detect erythema migrans or flulike symptoms, then prognosis with antibiotic therapy is excellent.

Option A (Amoxicillin) is incorrect. Amoxicillin is not used for prophylaxis except in pregnant patients. In all other cases, should the patient strongly desire antibiotic prophylaxis, doxycycline has been shown to be the most effective. Nevertheless, the first choice is observation.

Option B (Ceftriaxone) is incorrect. Ceftriaxone is used to treat the neurologic or cardiac complications of Lyme disease.

Option C (Enzyme-linked immunosorbent assay for Borrelia burgdorferi) is incorrect. Enzyme-linked immunosorbent assay is not reliable in the acute stage of Lyme disease, because antibodies take 6 to 8 weeks to develop.

Option E (Trimethoprim-sulfamethoxazole) is incorrect. Trimethoprim-sulfamethoxazole does not have a role in the management of Lyme disease.

High-yield Hit 1
Lyme disease
Lyme disease is caused by Borrelia spp. and is transmitted by Ixodes ticks
Figure 27.10 Transmission of Lyme disease.
Figure 27.11 Rash of erythema chronicum migrans on the leg in Lyme disease. (Courtesy of E Sahn.)
Lyme disease occurs in Europe, the USA and most continents of the world, and is named after the town in Connecticut, USA where the first cases were recognized in 1975. It is caused by Borrelia burgdorferi (USA) or other species of Borrelia. The natural cycle of infection takes place in mice and deer in whom it is transmitted by hard ticks of the genus Ixodes (Fig. 27.10). Human infection follows the bite of an infected tick (larval, nymph or adult form). In Europe and the USA, infection is more common in summer months when recreational exposure to infected ticks is more likely. Person-to-person transmission does not occur.
Erythema chronicum migrans is a characteristic feature of Lyme disease
The bacteria multiply locally, and after an incubation period of about 1 week fever, headache, myalgia, lymphadenopathy and a characteristic lesion at the site of the tick bite develop. The skin lesion is called 'erythema chronicum migrans' (Fig. 27.11), its name describing its main features. It begins as a macule and enlarges over the next few weeks, remaining red and flat, but with the center clearing, until it is several inches in diameter. In 50% of patients fresh transient lesions appear on the skin elsewhere in the body. Immunologic findings include circulating immune complexes and sometimes elevated serum IgM levels and cryoglobulins that contain IgM.

From Medical Microbiology 3E by Mims et al
High-yield Hit 2
Lyme disease commonly causes additional disease 1 week to 2 years after the initial illness
In 75% of untreated patients, in spite of antibody and T cell responses to the Borrelia, there are additional later manifestations of disease. These are seen from 1 week to more than 2 years after the onset of illness. The first of these manifestations to appear are neurologic (meningitis, encephalitis, peripheral neuropathy) and cardiologic (heart block, myopericarditis). The second of these manifestations to appear are arthralgia and arthritis, which may persist for months or years. Immune complexes are found in affected joints. These late manifestations are immunologic in origin and are probably due to antigenic cross-reactivity between Borrelia and host tissues. The Borrelia themselves are rarely detectable at this stage.
Lyme disease is diagnosed serologically and treated with antibiotic
The Borrelia are rarely seen in skin biopsies but can sometimes be isolated from biopsies obtained at an early stage, although this may take weeks. Thus, Lyme disease is primarily diagnosed on clinical presentation and known exposure. When indicated, serologic tests such as enzyme-linked immunosorbent assay (ELISA) and indirect fluorescent antibody (IFA) are useful. Specific IgM antibodies are detected 3-6 weeks after infection, and IgG antibodies at a later stage. Antigenic cross-reactivity may result in false positive results.
Doxycycline or amoxicillin are effective in treatment of early disease. Late disease, especially with neurologic complications, may require more aggressive therapy with intravenous penicillin or ceftriaxone for several weeks.
Prevention of Lyme disease is by avoidance of tick bites.

From Medical Microbiology 3E by Mims et al
A 33-year-old man presents to his physician with a week-long history of progressively worsening fevers, shortness of breath, and nonproductive cough. He has a history of human immunodeficiency virus (HIV) infection and has been taking highly active antiretroviral therapy (HAART). On examination, he is febrile and there are bilateral rales on auscultation of the chest. Laboratory examination reveals a CD4+ count of 180/μL and a lactate dehydrogenase (LDH) level of 430 U/L. Diffusing capacity for carbon monoxide (DLCO) is 62% of predicted. A chest X-ray (CXR) reveals diffuse, bilateral, interstitial infiltrates. What is the most likely cause of these findings?

Answer Choices Correct AnswerCorrect answer Your AnswerYour answer
A. Cryptosporidium spp
B. Mycobacterium avium complex (MAC)
C. Nocardia asteroides
D. Pneumocystis carinii
E. Toxoplasma gondii
Option D (Pneumocystis carinii) is correct. Although there are no truly specific signs or symptoms for Pneumocystis carinii pneumonia (PCP), there are a number of suggestive findings. An elevated LDH, decreased diffusing capacity for carbon monoxide (DLCO, and bilateral diffuse interstitial infiltrate are all characteristics of Pneumocystis carinii pneumonia (PCP). It occurs primarily after the CD4+ count has dropped below 200.

Option A (Cryptosporidium spp) is incorrect. Cryptosporidium presents as diarrhea in patients with HIV. Modified acid-fast stain of the stool demonstrates red-stained round oocysts.

Option B (Mycobacterium avium complex [MAC]) is incorrect. MAC presents with fevers, sweats, weight loss, and shortness of breath. There may also be tender hepatosplenomegaly. It typically does not occur until the CD4 count is below 50.

Option C (Nocardia asteroides) is incorrect. Nocardia are partially acid-fast, gram-positive rods that form branched hyphae. It commonly presents with pulmonary cavitation, as opposed to diffuse bilateral infiltrates. LDH is not usually elevated.

Option E (Toxoplasma gondii) is incorrect. Toxoplasma does not usually affects the lungs until the CD4+ count is below 40. It most commonly presents in the brain as multiple ring-enhancing lesions on computed tomography (CT).

High-yield Hit 1
Symptoms and Signs
Table 6-2. Opportunistic Infections in Immunocom-promised Hosts
Condition/lnfection Associated CD4 Count Symptoms and Signs Diagnostic Evaluation Treatment
Kaposi's sarcoma <500 Red or purple nodular skin lesions Biopsy Chemotherapy
Thrush <500 Thick white plaques on the oral mucosa Organisms visible on KOH treatment of exudate scrapings Fluconazole
Tuberculosis <500 Chronic cough, weight loss, fever, hemoptysis Acid-fast organisms in the sputum Pyrazinamide, isoniazid (INH), rifampin, ethambutol
Herpes simplex virus (HSV) <500 Painful skin vesicles Rapid antigen testing Acyclovir
Varicella zoster virus (VZV) <500 Pain and a cluster of vesicles in a dermatomal distribution None Varicella zoster immunoglobulin
Pneumocystis carinii pneumonia (PCP) <200 Dry cough with dyspnea

* (1) Chest radiograph shows interstitial infiltrates
* (2) Positive PCP sputum stain

Treat with trimethoprim-sulfamethoxazole or dapsone, and add steroids if the patient's PaO2 is <70
Toxoplasmosis <200 Symptoms of space-occupying intracranial lesion Multiple ring-enhancing lesions on CT with positive toxoplasmosis serologic tests Pyrimethamine, sulfadiazine, and folinic acid
Cryptococcosis <200 Symptoms of meningitis (headache, neck stiffness, etc) Positive serum or CSF Cryptococcus antigen Amphotericin B for 2 weeks, then lifelong fluconazole
Histoplasmosis <200 Meningitis or pneumonia, with exposure in the Midwest United States Positive urinary Histoplasma antigen Amphotericin B or itraconazole
Coccidiosis <200 Meningitis or pneumonia, with exposure in the Southwest United States DNA test Fluconazole or amphotericin B
Cytomegalovirus (CMV) <100 Retinitis, neuropathy, esophagitis, hepatitis Serologic study Treat with ganciclovir or foscarnet
Mycobacterium avium complex (MAC) <100 Fever, lymphadenopathy, abdominal pain, pneumonia, hepatosplenomegaly Acid-fast stain of sputum Treat with clarithromycin + ethambutol + sometimes rifabutin
Aspergillosis <100 Space-occupying lesion in lung, mucosa, or brain Biopsy, imaging Amphotericin B
CNS lymphoma (associated with Epstein-Barr virus [EBV]) <100 Headache, personality changes, focal neurologic signs

* (1) CT will show single enhancing lesion
* (2) Positive on CSF PCR assay for EBV

Chemotherapy
Progressive multifocal leukoencephalopathy (PML) <75 Dementia, visual problems, seizures, focal neurologic signs

* (1) Multiple nonenhancing lesions on CT
* (2) Positive PCR for JC virus in the CSF

None

From Rapid Review USMLE Step 2 by Lawlor
High-yield Hit 2

1. Adults
1. Acute retroviral syndrome: Can occur about 4 weeks after infection and includes a salmon-colored maculopapular rash, lymphadenopathy, splenomegaly, and malaise
2. Symptoms associated with opportunistic infections (Table 6-2)
2. Children: Will have developmental delay and recurrent or severe opportunistic infections. AIDS-defining illnesses in children include Pneumocystis carinii pneumonia, lymphocytic interstitial pneumonitis, and CNS lymphoma


From Rapid Review USMLE Step 2 by Lawlor
A 67-year-old man has experienced a 3-week history of malaise, myalgias, headaches, and low-grade fever. He has also noticed a weight loss of 2 kg (4 lb 6 oz) in this time. Over the last 2 days, he has begun to experience some shortness of breath on exertion. He was previously well and had his last annual health maintenance examination 4 months ago, which did not detect any abnormal findings. Physical examination reveals a holosystolic murmur best heard over the apex with the diaphragm and with the patient in the left lateral decubitus position. An echocardiogram demonstrates vegetations on the mitral valve. A group of three blood cultures all grow Streptococcus bovis. Following appropriate antibiotic therapy, what is the most appropriate investigation in this patient?

Answer Choices Correct AnswerCorrect answer Your AnswerYour answer
A. Colonoscopy
B. Coronary angiography
C. Cystoscopy
D. Head computed tomography (CT) scan
E. Purified protein derivative (PPD) skin test
Option A (Colonoscopy) is correct. This patient has infective endocarditis, caused by Streptococcus bovis. This organism tends to infect older individuals and those individuals with no previous structural heart disease. An important epidemiologic observation has been noted between S. bovis endocarditis and the presence of colonic neoplasia. Up to 32% of individuals who have S. bovis endocarditis were found to have a colonic neoplasm on investigation. Thus, it is important to have a screening colonoscopy as soon as possible. Negative colonoscopies should be followed up every 6 months with repeat colonoscopies.

Option B (Coronary angiography) is incorrect. This patient presents with shortness of breath on exertion most likely because of early congestive heart failure because of valvular pathology. There is nothing in the history to suggest coronary pathology.

Option C (Cystoscopy) is incorrect. Cystoscopy is used to evaluate the urethra and bladder. There are no urinary symptoms and no association with genitourinary neoplasms.

Option D (Head computed tomography [CT] scan) is incorrect. Patients with infective endocarditis are at increased risk of neurologic complications. These can range from embolic stroke to meningitis. However, this patient has no neurologic signs or symptoms suggestive of the need for CT scan.

Option E (Purified protein derivative [PPD] skin test) is incorrect. A PPD test is used as a screening test for latent tuberculosis. This patient has Streptococcus bovis and is not associated with Myobacterium tuberculosis.

High-yield Hit 1
DIAGNOSTIC CRITERIA FOR INFECTIVE ENDOCARDITIS
The modified Duke criteria for the diagnosis of infective endocarditis are described in Table 8-7.
Table 8-7. Modified Duke Criteria for the Diagnosis of Infective Endocarditis* Comments
Criteria Comments
Major criteria
Microbiologic
Typical microorganism isolated from two separate blood cultures: viridans streptococci, Streptococcus bovis, HACEK group, Staphylococcus aureus, or community-acquired enterococcal bacteremia without a primary focus
In patients with possible infective endocarditis, at least two sets of cultures of blood collected by separate venipunctures should be obtained within the first 1 to 2 hours of presentation. Patients with cardiovascular collapse should have three cultures of blood obtained at 5- to 10-minute intervals and thereafter receive empirical antibiotic therapy.

From Practical Guide to the Care of the Medical Patient 7E by Ferri
High-yield Hit 2

SPECIAL DIAGNOSTIC CONSIDERATIONS

1. Right-sided endocarditis

# Prosthetic valve endocarditis
# Streptococcus bovis endocarditis

1. Often associated with large bowel lesion, frequently carcinoma
2. A gastrointestinal work-up should be undertaken.


From Practical Guide to the Care of the Medical Patient 7E by Ferri
A 51-year-old man presents to the physician with the sudden onset of a productive cough, shortness of breath, fevers, and rigors since yesterday. He also complains of significant chest pain on coughing and deep inspiration. He has been otherwise well and does not take any regular medications. He has smoked one pack of tobacco daily for the last 30 years, drinks 10 to 20 g of ethanol weekly, and works as a lawyer. His vital signs are blood pressure (BP), 122/80 mm Hg; pulse, 120 beats/min; temperature, 39.2°C (102.5°F); and respirations, 32 breaths/min. There is dullness to percussion over the left posterior lung field, as well as increased vocal fremitus and crackles on auscultation of the area. A posteroanterior chest radiograph reveals localized left lower lobe infiltration. What is the most likely cause of these findings?

Answer Choices Correct AnswerCorrect answer Your AnswerYour answer
A. Haemophilus influenzae
B. Klebsiella pneumoniae
C. Mycoplasma pneumoniae
D. Staphylococcus aureus
E. Streptococcus pneumoniae
Option E (Streptococcus pneumoniae) is correct. This is a community-acquired pneumonia in an otherwise healthy individual. Tachypnea, tachycardia, and fever in concert with shortness of breath and productive cough are suggestive of the diagnosis, whereas radiographic findings are characteristic. In most cases of community-acquired pneumonia, specific microbiologic diagnosis is not attempted, because empiric therapy is effective. However, in epidemiologic studies, the most common bacterial cause of community acquired pneumonia in health adults is Streptococcus pneumoniae, causing anywhere from 30% to 60% of cases.

Option A (Haemophilus influenzae) is incorrect. Haemophilus influenzae is a common etiologic agent of pneumonia in elderly individuals, as well as individuals with chronic obstructive pulmonary disease (COPD), diabetes, renal failure, and congestive heart failure. Smokers are also at increased risk for H. influenzae, but Streptococcus pneumoniae is still more common overall.

Option B (Klebsiella pneumoniae) is incorrect. This agent is often associated with alcoholics who cough up current-jelly sputum.

Option C (Mycoplasma pneumoniae) is incorrect. This is the classic cause of atypical pneumonia, which presents with a subacute, dry cough, low-grade fever, and headaches. Chest X-ray usually reveals diffuse, patchy consolidation.

Option D (Staphylococcus aureus) is incorrect. Staphylococcus aureus is an infrequent cause of community-acquired pneumonia and is usually confined to the younger patient or elderly patient who are recovering from influenza. S. aureus is also associated with pulmonary cavitation.

High-yield Hit 1
Pneumonia
Figure 6-2 Abnormalities on chest radiograph in various types of pneumonia. Typical pneumonia often shows a pattern of lobar consolidation on radiographs. A, Lobar consolidation restricted to the right upper lobe. B, Consolidation of the right middle lobe with some involvement of the right upper lobe. C, Lobar consolidation of the right lower lobe. Note the clear diaphragmatic margin in right middle lobe consolidation, in contrast to the indistinct diaphragmatic border seen in right lower lobe consolidation. D, A diffusely infiltrative pattern is present in many cases of viral pneumonia (RSV in this case). E, A similarly diffuse pattern can be seen in atypical pneumonia caused by Mycoplasma pneumoniae infection.

1. Causes
1. Viral: RSV, adenovirus, parainfluenza, influenza, and enteroviruses
2. Bacterial (many cases of bacterial pneumonia also have viral disease)
* (1) S. pneumoniae: Most common cause of community-acquired pneumonia in otherwise healthy people.
* (2) Mycoplasmal pneumonia: Less severe, uncommon before 5 years of age. This is often called "walking pneumonia," and the chest radiograph often looks worse than the patient appears.
* (3) Chlamydial pneumonia: Found in infants at 2 to 3 months of age if their mothers had a chlamydial genitourinary infection.
* (4) Bacterial causes of pneumonia in children differ depending on the age group.
o (a) Neonatal period: Group B streptococci and Listeria monocytogenes.
o (b) Neonatal period to 5 years of age: S. pneumoniae, H. influenzae type b, S. aureus, and group A streptococci.
3. "Aspiration pneumonia" can occur following the aspiration of oral or esophageal contents, which can subsequently injure the lung
* (1) A serious situation involves the aspiration of gastric acid, which can produce cough, dyspnea, frothy sputum, and (in extreme cases) death.
* (2) Patients with aspiration injury are predisposed to the development of bacterial pneumonia, which can lead to clinical deterioration 2 to 3 days after the aspiration incident.
* (3) Treat aspiration injuries by establishing an airway, suctioning the airway, and providing oxygen and supportive care to maintain high oxygen saturation measurements.
2. Symptoms and signs
1. Patients typically have fever, chills, dyspnea, chest pain, and productive cough
* (1) Focal findings (decreased breath sounds, dullness, asymmetric crackles) suggest a bacterial cause.
* (2) Patients with pneumonia due to mycoplasmal or viral infection may have a low-grade fever, persistent dry cough, and malaise. They will have diffuse crackles on physical examination.
2. Presentation in children may involve more nonspecific constitutional complaints (fever, irritability, poor feeding, vomiting, lethargy)
3. Diagnostic evaluation: Chest radiographs to assess the extent of involvement and the possibility of pleural effusion. See Figure 6-2 for different abnormalities
4. Treatment
1. Bacterial pneumonia: Use IV cefuroxime or penicillin for inpatient cases, and amoxicillin for most outpatient bacterial cases. If H. influenzae or S. aureus is suspected cause, then amoxicillin/clavulanic acid should be used
2. Viral, mycoplasmal, or chlamydial pneumonia: Give supportive care as needed
3. Pleurocentesis can be performed for large pleural effusions if present


From Rapid Review USMLE Step 2 by Lawlor