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Dermatomyositis on Upper Extremities and Face and Nevus Achromicus in an 8-Year-Old Girl


A healthy 22-year-old man presents with asymptomatic dark streaks on his abdomen that occurred 1 week earlier while he was on a cruise in the western Caribbean. He says that he shaves the hair on his abdomen.

Case 1:

A healthy 22-year-old man presents with asymptomatic dark streaks on his abdomen that occurred 1 week earlier while he was on a cruise in the western Caribbean. He says that he shaves the hair on his abdomen.

What do you suspect?

A. Tinea corporis.
B. Tinea versicolor.
C. Insect bite reaction.
D. Phytophotodermatitis.
E. Shaving irritation.


Case 1: Lime phytophotodermatitis

Further questioning revealed that the patient had been squeezing lime into his drinks while he was on the cruise and had inadvertently applied some of the oils to his skin. This resulted in hyperpigmentation upon exposure to sunlight, D. Phytophotodermatitis resolves with time, from several weeks to a few months. Tinea features more scale. Insect bites are erythematous and pruritic. Shaving irritation would not be hyperpigmented.


Case 2:

For 4 months, a 73-year-old farmer has had a pruritic rash on one forearm. Because of his exposure to poison ivy on his farm, he was thought to have rhus dermatitis. A potent topical corticosteroid cream was prescribed, but the rash has not improved after 3 weeks of treatment.

What is the most likely cause of this patient’s rash?

A. Contact dermatitis to his watch.
B. Dermatophyte infection.
C. Cutaneous lupus.
D. Polymorphous light eruption.
E. Actinic keratoses.


Case 2: Tinea corporis


A potassium hydroxide evaluation confirmed the diagnosis of tinea corporis; one of the animals on the farm was the most likely source of the dermatophyte infection, B. A 1-week course of terbinafine coupled with application of a topical antifungal cream eradicated the rash. Polymorphous light eruptions and cutaneous lupus typically consist of erythematous patches and plaques that are more inflamed than the rash seen here. Actinic keratoses are more keratotic and are not pruritic. A contact dermatitis to his watch is possible, but the distribution of the rash does not match the area of skin exposed to his watchband.


Case 3:

A 25-year-old woman seeks evaluation of an itchy lesion on her neck. Almost a year earlier, a similar lesion occurred at the same site after she did yard work. Rhus dermatitis was suspected at that time; a topical corticosteroid was prescribed and the lesion resolved.

What is your clinical impression of this recurrent lesion?

A. Herpes simplex.
B. Contact dermatitis.
C. Impetigo.
D. Insect bite.
E. Fixed drug eruption.


Case 3: Herpes simplex type 1

Herpes simplex, A, was suspected, and antiviral therapy was started. A culture was positive for herpes simplex virus, type 1. Herpes simplex can mimic impetigo, but the viral infection recurs at the same site. Unlike the lesion seen here, fixed drug eruptions are usually not vesicular. Insect bites or contact dermatitis can resemble herpes simplex, although it would be unusual for them to recur in the same location.


Case 4:

For several days, a 73-year-old woman has had a pruritic eruption that is confined to her buttocks. She is widowed and has had no sexual contacts for many years. She is otherwise healthy.

Do you recognize this eruption?

A. Impetigo.
B. Trauma.
C. Herpes simplex.
D. Herpes zoster.
E. Cellulitis.


Case 4: Herpes simplex type 2

Antiviral therapy was started because herpes simplex, C, was suspected. A culture confirmed the diagnosis of herpes simplex type 2. Additional history revealed an exposure a long time ago. Impetigo is usually more crusted and is not hemorrhagic. Cellulitis is typically painful rather than pruritic. Trauma would not produce all of these lesions. Herpes zoster should be considered in the differential.

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