Uworld: 5-20

Front 1

30 year-old male
Admitted for DKA
Facial pain, headache
Nasal cavity contains necrotic eschar

Diagnosis
Diagnostic Procedure
Specific Organism
Treatment

Back 1

DM + Eschar = Mucormycosis (caused by Mucor, Rhizopus, Absidia)

Rhizopus has affinity for ketones and high blood glucose.

Proliferate in BV walls causing necrosis of downstream tissue.

Black necrotic eschar seen in nasal cavity = characteristic finding; can rapidly spread to CNS

Need histologic examination of affected tissue to make diagnosis (nonseptate hyphae with right angle branching)

Tx: Ampho B

Front 2

A new serologic test for prostate cancer is negative in 95% of patients who do not have the disease.

If the test is used in eight consecutive blood samples taken from patients without the disease, what is the probability of getting at least one positive test result?

Back 2

Each time the test is performed, there is a 0.95 (95%) probability that it will give a true-negative result and 0.05 (5%) probability it will give a false positive result.

To calculate change of all tests being negative, use multiplication rule for independent events:

Probability (all negative) = 0.95^8

Remember that total probability is always equal to 1.0 (1005). So probability that at least one test turns out positive is:

1-Probability (all negative)
=1-(0.95^8)

Front 3

What are the derivates of the aortic arch (1st-6th)?

Back 3

1st--MAXIMAL; maxillary artery

Second = Stapedial and hyoid aa

Third = C is third letter of alphabet-->Carotid artery

4th--4 limbs!--systemic circuln; on left: aortic arch, on right: proximal right subclavian artery

(there is no 5th)

6th arch: pulmonary aa and (on left only) ductus arteriosus

Front 4

Branchial arch derivates

Back 4

1-M's, T's--Mandible, malleus incus, muscles of MASTICATION, mylohyoid

2-S's--Stapes, styloid process, stylohyoid

3-Pharyngeal--stylopharyngeus

4th: cricothyroid
6th: everything in larynx except cricothyroid

Front 5

Branchial pouch derivatives

Back 5

1st: middle ear
2nd: palatine tonsil
3rd: INFERIOR PARATHY
4th: SUPERIOR PARATHY

Note 4th ends up being more superior than 3rd!

Front 6

Which branchial pouch:
Middle ear, eustachian tubes

Back 6

1st

Front 7

Which branchial pouch:
Superior parathyroids

Back 7

4th

Front 8

Which branchial pouch:
Inferior parathyroids

Back 8

3rd

Front 9

Which branchial pouch:
Epithelial lining of palatine tonsil

Back 9

2nd

Front 10

Which branchial pouch:
Thymus

Back 10

3rd

Front 11

72 year-old man
Brought to ER from nursing home
Altered mental status, flushing, fever
BP 60/20, HR 110
Blood cultures positive for E coli

Diagnosis
Pathophys

Back 11

Septic shock; most common source of E. coli bacteremia is urinary tract

Common predisposing factors: BPH, fecal incontinence, neurogenic bladder secondary to DM, frequent or indwelling catheterization

Front 12

What is the most common cause of UTI?

Back 12

E coli

Front 13

23 year-old male
Presents with confusion
Blood glucose 38 mg/dL
Elevated hepatic NADH

Diagnosis
Pathophys

Back 13

Low blood sugar and elevated NADH means a fuel other than glucose is being utilized by liver.

Likely EtOH. Hepatic EtOH catabolism produces NADH and inhibits gluconeogenesis.

Front 14

Which glands are responsible for salty sweat?

Back 14

Eccrine (merocrine) glands

Located throughout most of body excepts lips and glans penis.

Front 15

Which glands are responsible for smelly sweat?

Back 15

Apocrine

Front 16

Eczema:
Criteria for diagnosis
Triggers

Back 16

Red, weeping, crusted lesions with INTENSE PRURITUS. Pruritus is a hallmark of atopic dermatitis and the diagnosis cannot be made without it.

Note that eczema has a genetic component to it; it's triggered by various environmental factors, such as ingestion of certain foods or exposure to certain environmental irritants.

Patients will usually have elevated IgE levels, peripheral eosinophilia, high levels of cAMP PDE in leukocytes.

Front 17

What skin condition is associated with gluten enteropathy?

How does it differ from eczema?

Back 17

Dermatitis herpetiformis

Presents with pruritic VESICLES and plaques that occur on EXTENSOR SURFACES of extremities.

Can be treated with gluten-free diet and dapsone.

Front 18

What is the most common reason for elevated alpha-fetoprotein levels in pregnancy?

Back 18

Underestimation of gestational age

Front 19

How do AFP levels correlate with disease in pregnancy?

Back 19

If elevated AFP:
NT defects
Omphalocele, gastroschisis
Multiple gestation

If depressed AFP:
Down's syndrome

Front 20

How do hCG levels correlate with disease in pregnancy?

Back 20

hCG (synthesized by trophoblastic tissue);
inc'd with multiple gestation, hydatidiform mole, and choriocarcinoma

Front 21

56 year-old female
Undergoing chemotherapy
Develops frequent urination, suprapubic pain
Hematuria, dysuria

Pathophys
Prevention

Back 21

Patient must have been given a nitrogen mustard-based chemotherapeutic agent such as CYCLOPHOSPHAMIDE or one of its analogs (IFOSFAMIDE)

These agents are metabolized into acrolein which is toxic to uroeptihelial cells (TOXIC METABOLITES)

Prevent with MESNA which will bind and INACTIVATE toxic metabolites in urine.

Should also aggressively hydrate patient and irrigate bladder.

Front 22

Leak of radioactive material occurs at a plant. A number of workers are believed to have been exposed to heavy isotopes.

What should be immediately administered and why?

Back 22

Thyroid follicular cells take up ions via SODIUM IODIDE SYMPORTER (NIS).

IN addition to taking up iodine, also take up inorganic iodide, other ions, and radioactive iodine. Because of this each of these chemicals competitively inhibits each other (reduces their uptake).

So, to prevent uptake of radioactive iodine into follicular cells, you need to administer a competitor such as POTASSIUM IODIDE.

Front 23

Describe the formation of thyroid hormone and list where drugs act.

Back 23

Note: thionamides = propylthiouracil and methimazole

beta-blocker = propranolol

Front 24

45 year-old woman
Proximal interphalangeal and metacarpophalangeal joints are swollen/stiff bilaterally
Subcutaneous nodules palpated near nodule

Diagnosis
Antibody
Antibody AKA/Pathophys

Back 24

Rheumatoid arthritis

Would expect to see Rheumatoid Factor AKA an IgM antibody directed against Fc component of Self IgG.

Because of this RF binds IgG and forms immune complexes that circulate in serum.

Deposition of immune complexes on synovium and cartilage activates complement in those locations and contributes to chronic inflammn.

In other words: cartilage components serve as autoantigens that activate CD4+ cells, which stimulate B cells to secrete RF (IgM x Fc component of self IgG)

Front 25

What is schizoaffective disorder?

Back 25

Mood symptoms (major depressive, manic, or mixed) with concurrent symptoms of schizophrenia.

Pts must have at least 2 week period of psychotic syx (delusions or hallucinations) in ABSENCE of prominent mood syx.

(If had psychoses in presence of mood syx, would be bipolar disorder, manic episode w/psychotic features)

Front 26

Schizophrenia symptoms for under 1 month.

Back 26

Schizophreniform disorder

Front 27

Describe the symptoms of osteoarthritis.

Back 27

Use-dependent joint pain in weight bearing joints (as occurs at end of day); improves w/rest

<30 minutes morning stiffness

Front 28

Neisseria:
Drug of Choice

Back 28

PCN G
or
Ceftriaxone

Front 29

S. pneumo:
Drug of Choice

Back 29

Ceftriaxone

Front 30

Group B Strep:
Drug of Choice

Back 30

PCN G
Ceftriaxone

Front 31

H. flu:
Drug of Choice

Back 31

Ceftriaxone

Front 32

Listeria:
Drug of Choice

Back 32

Ampicillin

Front 33

Which Na+ blockers prolong action potential of ventricular myocytes?

Back 33

IA: Procainamide, QUinidine, Disopyramide

Front 34

Which Na+ blockers shorten ventricular myocyte action potentials?

Back 34

IB: Tocainamide, Lidocain, Mexiletene

Front 35

Describe the events that occur at each label.

Back 35

A) Aortic valve opens, fills
B) Aortic valve closes (end of systole); note: aortic valve closes as soon as LV pressure drops
C) Mitral Valve opens (this is where you'd hear the MV opening snap during M Stenosis)
D) Random point in diastole--note there's a pressure gradient between LA and LV (consistent with MStenosis; should be nearly equal!)
E) Atrial contraction during late diastole (MV still maximally open)

Front 36

53 year-old immigrant from Eastern Europe
Fever, weakness, dyspnea

Diagnosis
Pathologic Findings

Back 36

Rheumatoid Fever (Obviously)
But note vegetations, this is indicative of acute infective endocarditis (esp with syx). Can also occur in those with prosthetic heart valves.

The vegetations associated with bacterial endocarditis represent fibrin and PLT deposition at site of bacterial colonization

Front 37

Most common cause of acute infective endocarditis.

Back 37

S. aureus

Front 38

Mallory-Weiss Tears:
Pathophys
Metabolic Implications

Back 38

Mallory-Weiss teras occur near GE junction and are caused by high intragastric pressures assocd w/forceful vomiting against a tight LES.

Repetitive vomiting can occur w/alcohol consumption, leading to metabolic ALKALOSIS due to net loss of gastric secretions.

Front 39

What are the histologic signs of psoriasis?

Back 39

Hyperparakeratosis (orderly but anbnormal keratinizaiton of cells)
Acanthosis
Mitotic activity above basal layer
Reduced or absent striatum granulosum
Neutrophil clusters

Front 40

Where are psoriatic plaques likely to occur?

Back 40

Elbows, knees, gluteal cleft, glans penis, scalp

Front 41

Back 41

NNH represents number of people that need to be treated for one adverse event to occur.

NNH = 1/absolute risk

Treatment group: 60/80 = 75%

Placebo group: 38/76 = 60%

Absolute risk increase = Event rate (treatment) - Event rate (placebo)
=75%-50%=25%

Patients treated with drug X will have a 25% absolute increased risk of being dead at 3 months.

NNH = 1/ARI = 1/0.25 = 4

***NNH = 1/ARI***

Front 42

How does a bee sting result in a wheal?

Back 42

Venom of insect results in antibody class switching to IgE-->cross-linking-->mast cells and basophils release histamine

Front 43

Combat veteran that describes friends dying in cold and distant tone.

Coping mechanism?

Back 43

Isolation

Front 44

How does blood flow, arterial pressure, and arterial oxygen differ in the pulmonary and systemic circulations?

Back 44

Pulmonary circulation and systemic circulation are part of a continuous circuit.

Rate of blood flow must equal each other

However, arterial pressure and oxygen contents are considerably different both at rest and during exercise. (Lower pressure in pulmonary circulation, and obviously lower O2 content)

Front 45

Acute rejection of kidney transplant:
Cells involved
Typical histology

Back 45

Host T cells are sensitized against graft MHC antigens about one to four weeks following transplant

Histopathology will show mononuclear cells

Front 46

How does acute transplant rejection of a kidney differ from graft vs host disease?

Back 46

In Graft vs Host Dz, patients receive BM with foreign competent T lymphocytes. The recipient does not possess competent T lymphocytes.

As such, graft T cells are sensitized against host MHC antigens in this process.

Kidney transplantation does not require transplant of foreign T lymphocytes.

Front 47

What muscles comprise the rotator cuff?

Back 47

SITS
Supraspinatus
Infraspinatus
Teres minor
Subscapularis

Front 48

Which tendon of the rotator cuff is most likely to be injured?

Back 48

Tendon of supraspinatus

Front 49

How is supraspinatus pathology identified?

Back 49

Simultaneous abduction and flexion of the arm at the shoulder (have patient abduct arm, flex forearm with thumb facing floor, then apply pressure to arm)

aka "the empty can test"

Front 50

When does stable angina become apparent?

When does it become unstable?

Back 50

Fixed atherosclerotic plaque obstructing ≥75% of coronary artery lumen

Becomes unstable when plaque undergoes acute change.

Front 51

What is acute coronary syndrome?

Back 51

Unstable angina, MI, and sudden cardiac death (likely due to acute plaque change of stable plaque)

Front 52

Which Na+ blockers shorten ventricular myocyte action potentials?

Back 52

IB: Tocainamide, Lidocain, Mexiletene

Front 53

Early diastolic murmur heard at left sternal border.

Back 53

Aortic regurgitation

Front 54

What is diastolic heart failure?

How does this affect LVEDP/LVEDV?

Back 54

Dec'd ventricular diastolic compliance, but normal ventricular contractile performance

As a result, left end diastolic pressure must be increased.

Front 55

What is systolic heart failure?

How does this affect LVEDP/LVEDV?

Back 55

Dec'd ventricular contractile performance (dec'd ejection fraction)

Requires an increase in LVEDP to create an abnormally high LVEDV and achieve a near-normal stroke volume.

Front 56

What are the metabolic effects of aspirin overdose (acute vs chronic)?

Describe pH, PaCO2, plasma HCO3.

Back 56

Acute: Shortly after OD, ASA stimulates respiratory center and pt begins hyperventilating-->RESPIRATORY ALKALOSIS

After a few hours, acid products will accumulate in blood and patient will undergo METABOLIC ACIDOSIS

Together, this becomes a mixed respiratory alkalosis-metabolic acidosis.

pH may be normal
PaCO2 should be decreased (not a compensatory response; due to hyperventilation)

plasma HCO3 should be low (indicating metabolic alkalosis; not compensation!)

Front 57

Lab values of hemophilia.

Back 57

Prolonged PTT
Normal PT (prothrombin time)
Normal TT (thrombin time)
Normal bleeding time

Front 58

Hemophilia:
Mode of inheritance

Back 58

X-linked recessive

Front 59

PT vs PTT:
When would either be prolonged?
Give examples.

Back 59

PT: deficiencies of factors II, V, VII, X, fibrinogen (most commonly due to warfarin therapy)

PTT: includes factors VIII-XII (has more, but let's be high yield, okay??); this is the one that's prolonged in hemophilia (Factors VIII, IX)

Front 60

When is bleeding time prolonged?
Give an example.

Back 60

When there's a qualitative or quantitive defect in platelets.

Often will see mucocutaneous hemorrhage (recurrent epistaxis, gingival hemorrhage), cutaneous ecchymoses, petechiae.

Ex: vWDz, NSAID use

Front 61

When is thrombin time prolonged?

Back 61

Deficient or defective fibrinogen

Front 62

Describe renal filtration/reabsorption/secretion of:
Creatinine
Glucose
Inulin
Mannitol
PAH
Sodium
Urea

Back 62

Front 63

What cells are TdT+?

Back 63

Immature B/T cells (Precursor cells)

Front 64

Infant develops vomiting after birth
Mother notices odor of burnt sugar in diapers

Which amino acids should be restricted in infant's diet?

Back 64

Isoleucine
Leucine
Valine

Front 65

What is the effect of nitrite poisoning on the partial pressure of oxygen in arterial blood?

Back 65

No effect bc methemoglobin does not affect dissolved O2 in plasma (it's unrelated to Hgb).

Front 66

Infant with hypotonia and seizures
Unable to oxidize very long chain fatty acids

Diagnosis
Effect on presentation

Back 66

Peroxisome disease where peroxisomes are either absent or nonfnal; VLCFAs cannot undergo mitochondrial beta-oxidation, need peroxisomes to be metabolized.

Inability to break down VLCFA --> improper CNS myelination

Front 67

Draw and label a diagram of a tRNA molecule.

Back 67

5' END HAS TERMINAL GUANOSINE and DOES NOT participate in amino acid or mRNA binding.

Also note that anticodon is located at top part of molecule; it recognizes and binds the mRNA codon, assuring placement of the proper amino acid in the growing polypeptide chain.

Front 68

What's an arthropod?

Back 68

Tick--betware of Borrelia burgdorferi!

Front 69

What structures comprise the foregut?
Arterial supply?

Back 69

Esophagus through second part of duodenum, liver, gallbladder, pancreas

All supplied by celiac trunk

Front 70

What organ is supplied by an artery of the foregut although it is not a foregut derivative?

Back 70

Spleen--it forms from mesodermal dorsal mesentary.

Splenic artery is a branch of the celiac trunk (primary blood supply of foregut)

Front 71

How do vitamin B12 and folate acid deficiencies differ clinically?

Back 71

Both will cause megaloblastic anemia, but only a B12 deficiency will result in decreased proprioception and vibration sense.

Note: if megaloblastic anemia due to B12 is mistakenly treated with folate alone, the neurologic dysfn can worsen!