Dermclinic: A Photo Quiz to Hone Dermatologic Skills (July 2005)

Case 1: A 5-year-old girl is brought for evaluation of an asymptomatic inflamed streak on one leg that has been present for several weeks. She is otherwise healthy and takes no medications. What does this look like to you? A. Psoriasis. B. Contact dermatitis. C. Lichen planus. D. Lichen striatus. E. Lichen sclerosus. Answer on next page   , Case 1 Answer: The child has lichen striatus, D, a self-limited papular eruption that occurs primarily in children and affects twice as many girls as boys. The eruption persists for months before resolving spontaneously. No treatment is necessary, although some lesions respond to topical corticosteroids. Psoriasis consists of discrete scaly lesions. Contact dermatitis is pruritic. Lichen planus features discrete flat-topped polygonal purple papules. Lichen sclerosus is characterized by hypopigmented coalescing macules.   Case 2 on next page , Case 2: For several months, a 63-year-old woman has noticed discrete patches of asymptomatic thick, crusty scale on her scalp. Over-the-counter dandruff shampoos have had no effect on the condition. Which of the following do you suspect? A. Psoriasis. B. Seborrheic dermatitis. C. Impetigo. D. Candidiasis. E. Pityriasis amiantacea. Answer on next page , Case 2 Answer: Pityriasis amiantacea, E, is characterized by thick, asbestoslike adherent crusts that may be localized or spread diffusely through the scalp; it is also associated with nonscarring hair loss. This condition is thought to be a localized altered immune response to seborrheic dermatitis or psoriasis. Because the scale is so thick, it is difficult for topical therapies to penetrate. Overnight application of keratolytic agents will aid penetration. (Advise patients to use a shower cap.) Ketoconazole shampoos are also effective. Psoriasis usually features inflammation and pruritus. Seborrheic dermatitis does not produce crusts as thick as this patient’s. Crusts associated with impetigo and candidiasis are thin, flat, and honey-colored. None of these conditions is associated with hair loss.   Case 3 on next page , Case 3: For several days, a 45-year-old man has been bothered by a progressive tender rash on the buttocks. He has taken a cephalosporin plus rifampin for the past 2 days, but there is no improvement. What is your clinical impression? A. Methicillin-resistant Staphylococcus aureus infection. B. Streptococcal impetigo.  C. Candidiasis. D. Herpes zoster (shingles). E. Bullous pemphigoid. Answer on next page , Case 3 Answer: This patient has herpes zoster (shingles), D,  which features grouped vesicles on an erythematous base. Neither staphylococcal, streptococcal, nor candidal infection produces clear, intact vesicles. Bullous pemphigoid is typically pruritic, not tender.   Case 4 on next page , Case 4: A 66-year-old woman presents for evaluation of a pruritic eruption on the trunk of 10 days’ duration. She is otherwise healthy and for several years has taken no medication but hormone replacement therapy and a multivitamin. To what do you attribute the patient’s rash? A. Localized bullous pemphigoid. B. Impetigo. C. Candidiasis. D. Insect bite. E. Contact dermatitis. Answer on next page , Case 4 Answer:  A biopsy confirmed the diagnosis of localized bullous pemphigoid, A, a rare, relatively benign autoimmune disease that preferentially affects elderly persons. An ultrapotent topical corticosteroid, such as clobetasol, is effective for this condition. Neither impetigo nor candidiasis produces the type of tense blisters characteristic of bullous pemphigoid. Insect bites may resemble the eruption seen here; histologic studies and immunofluorescence would be required to make the diagnosis. Contact dermatitis might be considered, although the patient has no exposure history, and the discrete nature of the lesions make this diagnosis less likely