What is responsible for this 4-month rash?

A 44-year-old female presented for evaluation of an itchy eruption on the shins of 4 months duration. She is otherwise healthy. 

What is responsible for her rash?

A. Stasis dermatitis

B. Psoriasis

C. Lichen planus

D. Disseminated superficial actinic porokeratoses

E. Lichenoid keratosis

Bonus Question: Where else could you look for possible cutaneous clues to help make a diagnosis? What other condition has been associated with this rash?

(Answer and discussion on next page)

Answer: Lichen planus

A biopsy confirmed the diagnosis of lichen planus, a condition of uncertain etiology. Typically self-limited, it resolves over several months but can last longer. Oral lesions on the buccal mucosa can help confirm the diagnosis. This condition has been associated with hepatitis C.

Stasis dermatitis should be diffuse and associated with leg swelling. Although possible, psoriasis is usually scalier in appearance. Disseminated superficial actinic porokeratoses is usually asymptomatic. Lichenoid keratoses are usually less extensive but can be considered a possibility.