Kaplan Diagnostic Tests; Dermatology

Front 1

For which clinical condition(s) is diascopy commonly used?

Back 1

Diascopy is the best initial test for erythematous lesions. It is a fancy way to see if the lesion blanches (turns white) when pressed. Diascopy, where a clear plastic glass slide is pressed over the skin, is used to determine if an erythematous skin lesion is due to vasodilatation or extravasation of RBCs via damaged blood vessels.

Front 2

What do you look for under diascopy?

Back 2

If the skin blanches with diascoopy, the erythema is caused by vasodilatation. Simple vasodilation is caused by viral diseases, drug reactions, and insect bites. If the lesion persists under diascopy, the redness is caused by extravasation of erythrocytes via damaged blood vessels, as seen with vasculitic and purpuric lesions.

Front 3

For which clinical scenario(s) is excision skin biopsy indicated?

Back 3

Excision biopsy is a skin biopsy technique where the full thickness of a lesion is removed. preferably intact.

Front 4

For which condition is excision skin biopsy always the right answer?

Back 4

Excision biopsy is always the right anwer for the workup of a lesion suspected of being a malignant melanoma.

Front 5

For which clinical scenario(s) is direct immunofluorescence the best test?

Back 5

Direct immunofluorescence (DIF) of skin biopsy samples is used to diagnose skin disorders of immunologic origin. The DIF test looks for the presence and staining pattern of immunoglobins (IgG, IgM, IgA), C3, and fibrinogen in the skin. For example, it is useful for differentiating between pemphigus vulgaris and bullous pemphigoid.

Front 6

What is seen under the microscope with direct immunofluorescence (skin)?

Back 6

Pemphigus vulgaris: IgG and C3 are seen between epidermal cells.

Bullous pemphigoid: IgG and C3 at dermo-epidermal junction.

Front 7

For which clinical condition(s) is fungal culture the most accurate test?

Back 7

A fungal culture is the most accurate test for diagnosing superficial fungal infections of the body. Examples are tinea, onychomycosis, and fungal vaginitis.

Front 8

When is fungal culture the best initial step?

Back 8

Never; although a culture is very accurate, it is never teh best initial test. A fungal infection is diagnosed primarily by visual appearance and confirmed by KOH prep.

Front 9

What is the management for fungal skin infection?

Back 9

Depending on teh location of the infection, topical or oral antifungals are the management of choice. Onychomycosis (nail bed) and tinea capitis (scalp) need to be treated with oral antifungals (terbinafine or itraconazole). All fo the other fungal infections of the skin may be treated with topical medications such as ketoconazole, clotrimazole, nystatin, or ciclopirox.

Front 10

What is skin scraping and mineral oil mount?

Back 10

The skin scraping and mineral oil mount is used to aid in teh diagnosis of scabies. Mineral oil is applied over teh suspected lesion to enhance teh viewing of a burrow. The skin is scraped adn viewd under teh microscope. The skin cells remain intact, mite feces are preserved, adn the mites remain motile and alive in mineral oil.

Front 11

When is skin scraping and mineral oil mount the answer?

Back 11

Look for a patient with an itchy (pruritic) skin rash. There will be small "burrows" visible, particularly in the web spaces of the hands and feet. There may also be a history of sexual contact and genital or breast involvement as well.

Front 12

What is an adjuvant test often used for an itchy skin rash?

Back 12

A KOH wet mount is prepared from teh skin scrapings and the slide is heated, breaking up the tissue to reveal any mites hiding under a lump of squamous cells.

Front 13

For which clinical scenario(s) is patch testing indicated?

Back 13

Patch testing is used to determine the allergen responsible for allergic contact dermatitis after conservative measures like removing the supposed offending agent and a trial of topical therapy fail.

Front 14

What important distinction must be made before utilizing a patch test?

Back 14

It is important to determine if the patient's contact dermatitis is caused by an irritant or an allergy.

NOTE: Patch testing is not useful for irritant contact dermatitis because irritant dermatitis is not an immunologically mediated response.

Front 15

What is wood's light examination?

Back 15

A wood's light examination uses a UV light to diagnose certain infections of the skin caused by yeast, bacteria, or dermatophytes. It is also used to detect pigment changes in the skin. For example, it detects loss of pigment in fair-skinned individuals affected with a depigmentation disorder, such as vitiligo

Front 16

What are some organisms that will fluoresce under Wood's light?

Back 16

The following organisms fluoresce:

1) The yeast Pityrosporum ovale will fluoresce yellow.

2) The bacterium Corynebacterium minutissimum will fluoresce a bright coral red.

3) The dermatophyt Microsporum canis will fluoresce blue-green in teh scalp but not on glabrous skin. However, in the US, tinea capitis is most commonly caused by Trichophyton tonsurans, which does not fluoresce under Wood's light.