“Are we there yet?”

Abstract

The approach to clinical conundrums by an expert clinician is revealed through presentation of an actual patientA 62-year-old man with psoriasis for more than 30 years presented to the emergency department with a scaly, pruritic rash involving his face, trunk, and extremities that he had had for the past 10 days. The rash was spreading and not responding to application of clobetasol ointment, which had helped his psoriasis in the past. He also reported mild pharyngitis, headache, and myalgias.A patient with a chronic skin condition presenting with a new rash means the clinician must consider whether it is an alternative manifestation of the chronic disorder or a new illness. Psoriasis takes many forms including guttate psoriasis, which presents with small, droplike plaques and frequently follows respiratory infections (particularly those caused by Streptococcus). Well-controlled psoriasis rarely transforms after 3 decades, so I would consider other conditions. The tempo of illness makes certain life-threatening syndromes, including Stevens-Johnson, toxic shock, and purpura fulminans, unlikely. An allergic reaction, atopic dermatitis, or medication reaction is possible. Infections, either systemic (eg, syphilis) or dermatologic (eg, scabies), should be considered. Photosensitivity could involve the sun-exposed areas, such as the extremities and face. Seborrheic dermatitis can cause scaling lesions of the face and trunk but not the extremities. Vasculitis merits consideration, but dependent regions are typically affected more than the head. Mycosis fungoides or a paraneoplastic phenomenon could cause a diffuse rash in this age group.The patient had diabetes mellitus, hypertension, diverticulosis, and depression. Three months earlier he had undergone surgical drainage of a perirectal abscess. His usual medications were lovastatin, paroxetine, insulin, hydrochlorothiazide, and lisinopril. Three weeks previously he had completed a 10-day course of trimethoprim/sulfamethoxazole for an upper respiratory infection. Otherwise, he was taking no new medications. He was allergic to penicillin. He denied substance abuse, recent travel, or risk factors for human immunodeficiency virus (HIV) infection. He worked as an automobile painter, lived with his wife, and had a pet dog.Physical examination revealed a well-appearing man with normal vital signs. His skin had well-defined circumscribed pink plaques, mostly 1-2 cm in size, with thick, silvery scales in the ears and on the dorsal and ventral arms and legs, chest, back,