Psoriasis photo affects the elbows

A 45-year-old woman presents with a localized area of erythematous scaly patches that comes and goes and typically affects the elbows. The likely diagnosis is.........

• A) pityriasis rosacea
• B) mycosis fungoides
• C) tinea corpora
• D) nummular eczema
• E) psoriasis

The answer is E. (Psoriasis) 

Psoriasis usually manifests itself as erythematous scaly patches that affect the knees or elbows. More severe cases can involve multiple areas over the entire body. Extensor surfaces are predominantly affected. Nail pitting may be present. The condition appears to be hereditary. Diagnosis is usually based on clinical findings. Skin biopsy may be helpful for definitive diagnosis. Treatment consists of topical steroids, intralesional steroids, tar preparations, anthralin, tazarotene, and calcipotriene.