Dermatology MCQs 10 For USMLE PLAB DHA MOH Medical Exams

Dermatology MCQs 10 For USMLE PLAB DHA MOH Medical Exams

Most patients with bullous pemphigoid respond well to which of the following?

A. Cycloheximide.

B. Prednisone. ✅

C. Nonsteroidal anti-inflammatory agents.

D. Penicillamine.

E. Cyclosporine.

Question Explanation:

Prednisone is the treatment of choice in the majority of patients with bullous pemphigoid, a chronic, benign eruption of tense bullae on normal or reddened skin, seen mainly in the elderly.

A 37 year old HIV positive male is administered antimicrobial prophylaxis for Pneumocystis carinii. He subsequently develops Stevens Johnson syndrome. The medication most often prescribed is which of the following?

A. Aerosilized pentamidine

B. Dapsone

C. Trimethoprim-sulfamethoxazole ✅

D. Amphotericin

E. Vancomycin

Question Explanation:

Side effects of trimethoprim sulfamethoxazole include the development of Stevens-Johnson syndrome, rash, and hepatitis. While dapson (B) and aerosilized pentamidine (C) have also been used in the prophylaxis of Pneumocystis carinii infection, they do not produce Stevens Johnson syndrome or erythema multiforme.

A patient on total parenteral nutrition develops alopecia and a facial rash. What is the most likely deficiency?

A. Vitamin A

B. Chromium

C. Copper

D. Zinc ✅

E. Selenium

F. Manganese

Question Explanation:

During chronic total parenteral nutrition, deficiencies in trace elements may manifest. Deficiency in zinc can produce a rash; poor wound healing, alopecia, and taste and smell disturbances. Copper deficiency may manifest as an iron-unresponsive anemia or pancytopenia. Chromium deficiency may produce glucose intolerance. Selenium deficiency may present as proximal neuromuscular weakness. Manganese deficiency may present with weight loss, altered hair pigmentation, and low serum triglycerides. Vitamin A deficiency will manifest with night blindness, keratomalacia, Bitot's spots, conjunctival xerosis, respiratory tract infections, etc.

All of the following are reliable tests to diagnose mastocytosis EXCEPT

A. Biopsy of spleen and liver with special staining of granules.

B. 5-hydroxyindolacetic acid level. ✅

C. bone-marrow biopsy.

D. Elevated plasma histamine levels.

E. Skin biopsy with special staining of granules.

Question Explanation:

5-hydroxyindolacetic acid is a by-product of serotonin and is present in excess amounts in carcinoid syndrome. This syndrome causes flushing, diarrhea, and, sometimes, wheezing. Mastocytosis is a systemic disorder which produces degranulation of excess mast cells and symptoms of pruritis, diarrhea, and rash. Skin biopsy should be stained for basophils and histamine. Elevated plasma histamine and elevated urine histamine levels are the hallmark of mastocytosis. Bone-marrow biopsy would reveal nodular, paratrabecular infiltrates of mast cells. Biopsy of the spleen and liver with special staining for basophils and histamine would diagnose mastocytosis.

All of the following have been associated with atopic dermatitis EXCEPT

A. Animal dander.

B. Steroids. ✅

C. Grass.

D. Detergent.

E. Perfume.

Question Explanation:

Steroids are used to treat atopic dermatitis and are not causal. All of the other antigens have been associated with atopic dermatitis.

A 51-year-old has a well-marginated, erythematous plaque with silvery white surface scales on his elbow. He also has arthritis and onycholysis with pitting of the nail plate. Which one of the following is the most likely diagnosis?

A. Psoriasis ✅

B. Impetigo

C. Lichen planus

D. Pemphigus Vulgaris

E. Seborrheic dermatitis

Question Explanation:

Psoriasis is chronic non-pruritic skin disorder associated with arthritis, pitting of the nails, and thickening of the nail plate with accumulation of subungual debris. Its distribution includes extensor surfaces such as knees, elbows, and buttocks. Treatment includes topical steroids, ultraviolet light, and, in severe cases, methotrexate.

Pemphigus Vulgaris is characterized by extensive flaccid blisters and mucocutaneous erosions. Lichen planus resembles psoriasis, though it is pruritic and sometimes accompanied by oral lesions. Impetigo is a superficial infection of the skin by S. aureus or beta-hemolytic streptococci. The erosions are "honey-colored crusted" lesions and tend to develop near superficial traumatic lesions and in areas exposed to the sun. Seborrheic dermatitis is a chronic noninfectious process characterized by erythematous patches with greasy yellowish scales.

Which of the following statement is false regarding contact dermatitis?

A. Local steroids are not useful ✅

B. Skin testing is useful

C. Systemic steroids could be used

D. Can be due with plant exposure

E. Topical antipruritics may help relieve itching

Question Explanation:

Contact dermatitis (CD) is acute inflammation of the skin caused by irritants or allergens. The primary symptom is pruritus. Skin changes range from erythema to blistering and ulceration, often on or near the hands but occurring on any exposed skin surface. Diagnosis is by exposure history, examination, and sometimes skin patch testing. Treatment entails antipruritics, topical corticosteroids, and avoidance of causes. CD is treated by avoiding the trigger: patients with photosensitive CD should avoid exposure to sun. Topical treatment includes cool compresses (saline or Burow's) and corticosteroids; patients with mild to moderate cases are given mid potency topical corticosteroids (eg, triamcinolone 0.1% ointment or betamethasone valerate cream 0.1%). Oral corticosteroids (eg, prednisone 60 mg once/day for 7 to 14 days) can be used for severe blistering or extensive disease.

Symmetrical, depigmented areas on the arms and legs in a 24-year-old female are most likely to be associated with?

A. Diabetes mellitus

B. Hypoparathyroidism

C. Scleroderma

D. Pernicious anaemia ✅

E. Systemic lupus erythematous (SLE)

Question Explanation:

She has vitiligo and consequently is 15 times more likely to be suffering from an additional autoimmune condition. Although hypoparathyroidism may be an associated autoimmune condition, pernicious anemia occurs more frequently.

Vitiligo may be a component of the polyglandular autoimmune syndrome which includes type 1 diabetes, autoimmune adrenal insufficiency, and autoimmune thyroid disease. SLE causes post-inflammatory hypopigmentation and scleroderma is not associated.

A sixteen-year-old girl, who is known to be allergic to bee stings, presents after suffering a bee sting. Which of the following is the most likely clinical outcome?

A. Facial rash

B. Localized oozing and swelling

C. Type I reaction ✅

D. Stridor

E. Widespread urticaria

Question Explanation:

A patient with an allergy to bee stings is likely to develop a type I reaction to a bee sting and therefore anaphylactic shock. Generalized urticaria, loss of consciousness, facial rash and stridor may be part of anaphylaxis. In this patient, the correct answer would be type I reaction.