Exfoliative dermatitis. Erythroderma can be a sign of a significant underlying disorder

64-year-old man presented with a 3-week history of a diffuse, pruritic rash that had started on his trunk and then spread to his entire cutaneous surface, including the palms of his hands and soles of his feet. Physical examination revealed widespread fine scaling and diffuse erythema. Generalized lymphadenopathy was noted. No fever, hair loss, onycholysis, or nail shedding was detected. The patient had neither a personal history of skin disorders or, specifically, atopic eczema or psoriasis nor a family history of eczema or psoriasis. He also had no history of malignancy and was taking no medications. The patient's complete blood cell count with differential was unremarkable. He was treated with moisturizers, topical corticosteroids, and antihistamines and was advised to avoid possible irritants. One week later, the patient returned because of a worsening of his erythroderma. He also reported malaise and chills. Three 4-mm biopsy specimens were obtained from representative areas (ie, back, arm, and abdomen), and a 2-week course of oral corticosteroids was prescribed. The erythroderma greatly improved but worsened shortly after the steroid dose was tapered. The specimens showed psoriasiform hyperplasia with features suggestive of psoriasis vulgaris. The patient was treated with 25 mg of oral acitretin once a day. His erythroderma slowly resolved over 6 months, at which time the acitretin dose was tapered. The patient reported no recurrence of the erythroderma.