Dermatology MCQs 2 For USMLE PLAB DHA MOH

Dermatology MCQs 2 For USMLE DHA MOH HAAD SLE AMC Exam

A 27-year-old male has noticed a gradual asymptomatic loss of color on his penis and several areas of depigmentation on his scalp and face. He takes no medications and is not exposed to any chemicals. There is a family history of similar dermatological signs. What is the most likely diagnosis?

A. Herpes zoster

B. Eczema

C. Ichthyosis vulgaris

D. Condyloma acuminatum

E. Vitiligo ✅

Question Explanation:

Vitiligo is a pigment disorder characterized by asymptomatic lesions that develop slowly over areas of the skin. The cause is unknown, but vitiligo occurs in people of all races and ages and often runs in families. It has been associated with immune disorders including Grave's disease, diabetes mellitus, and pernicious anemia. Herpes zoster causes painful vesicular lesions in a dermatomal distribution. Ichthyosis vulgaris is an autosomal dominant disorder inherited as scaly skin disease. Condyloma acuminatum are lesions due to HPV and manifest as single/multiple, sessile/pedunculated red papillary excrescences and occur on prepuce or coronal sulcus. Eczema is a chronic, atopic dermatitis characterized by pruritus, erythema, and crusting. Lichenification can be seen secondary to chronic scratching.

Dermatitis herpetiformis is associated with

A. G6PD deficiency

B. IgA deposition in the Stratum corneum.

C. Circulating autoantibodies.

D. Herpes simplex.

E. Celiac disease. ✅

Question Explanation:

The association of dermatitis herpetiformis with celiac disease provides a clue to its pathogenesis. Genetically predisposed individuals develop IgA antibodies to dietary gluten (derived from the wheat protein gliadin). The antibodies cross-react with reticulin, a component of the anchoring fibrils that tether the epidermal basement membrane to the superficial dermis. IgA deposits in the upper dermis in dermatitis herpetiformis.

Which one of the following conditions is characterized by erythema chronicum migrans?

A. Stevens-Johnson syndrome

B. Syphilis

C. Infection with Borrelia burgdorferi ✅

D. Trichinosis

E. Streptococcal infections

Question Explanation:

Erythema chronicum migrans, an annular spreading lesion often associated with central clearing is the hallmark of Lyme disease, which is caused by infection with B. burgdorferi. None of the other conditions is associated with this particular skin lesion. Stevens-Johnson syndrome is a form of erythema multiforme, usually resulting from adverse reactions to particular drugs.

In her garden, 75-year-old woman developed a maculopapular eruption on her hands, nose, and forehead. Her eyes became very sensitive to light. The patient's temperature and vital signs were normal. The rash became vesicular, crusty, and mildly pruritic. This patient was given a two-week course of tetracycline for an atypical pneumonia recently. What is the most likely diagnosis?

A. Poison ivy dermatitis

B. Insecticide allergy

C. Sporotrichosis

D. Tetracycline drug-induced photosensitivity reaction ✅

E. Erythema multiforme major

Question Explanation:

This woman suffers from tetracycline-induced photosensitivity reaction. Tetracycline also causes photophobia and, if given again, can cause a more severe, prolonged course. Sporotrichosis is a fungal infection caused by exposure to thorns. The rash is not typical for Sporotrichosis. If the patient has this disease, treatment would be potassium iodide. Insecticide exposure would not cause photophobia. It would cause cholinergic symptoms such a pin-point pupils, dryness of skin, and palpitations. A contact dermatitis from poison ivy exposure would cause more pruritus, and the rash would be more erythematous. Erythema multiforme major is a dermatologic condition that also involves mucus membranes.

A 31-year-old man is concerned about hair loss. You diagnose him as having non-scarring alopecia. Which is not the treatment for non-scarring alopecia?

A. Intralesional triamcinalone ✅

B. Hair transplantation

C. Minoxidil

D. Spironolactone

E. Finasteride

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