What is the most likely cause of these itchy bumps?

A 34-year-old woman has been bothered for 1 month by itchy bumps on her elbows and knees.

Which of the dermatoses in your differential is the most likely culprit?

A. Psoriasis.

B. Lichen planus.

C. Granuloma annulare.

D. Dermatitis herpetiformis.

E. Contact dermatitis.

(Answer on next page.)

Answer: Granuloma annulare

The suspected diagnosis of granuloma annulare, C, was confirmed by a biopsy. The presence of pruritus in this usually asymptomatic eruption was somewhat misleading, but the lesion’s location—overlying the joints of a female patient—was appropriate.

Psoriasis was ruled out by the appearance of the lesions; psoriatic eruptions are generally larger and more scaly. Lichen planus typically features purplish, flat plaques. 

Dermatitis herpetiformis lesions usually are masked by excoriations caused by scratching the highly pruritic eruptions of this disease. Contact dermatitis lesions tend to be more scaly and less discrete than those seen here