12 www.JAAPA.com Volume 28 • Number 7 • July 2015 DERMATOLOGY DIGEST A 61-year-old man was brought to the hospital dermatol- ogy department with a pruritic eruption that started about 2 weeks after he was admitted to another hospital for renal failure and hematemesis. The eruption started on his face, extended downwards, and continued to spread. While he was hospitalized, he was empirically treated for presumed impetigo with oral trimethoprim/sulfamethox- azole DS and mupirocin 2% topical cream for 2 weeks with no improvement. Physical examination revealed multiple tense bullae and vesicles on an erythematous background interspersed with annular, erythematous plaques with dusky red centers (Figure 1). He had numerous crusted erosions distributed on his upper back and extending to his mid-back, upper chest, and face. He had no oral or extremity involvement. THE LIKELY DIAGNOSIS IS: • porphyria cutanea tarda • pemphigus vulgaris • bullous pemphigoid • bullous erythema multiforme DISCUSSION A punch biopsy was taken from a representative and rela- tively new lesion on his chest and was consistent with bullous pemphigoid. Although direct immunofluorescence was negative, the patient was diagnosed with bullous pemphigoid based on his history and clinical findings. The lesions were treated with clobetasol ointment twice daily with good effect. Bullous pemphigoid is an autoimmune blistering disease in which autoantibodies attack the hemidesmosomal proteins BP180 and BP230 found at the dermoepidermal junction of the skin. 1 The condition causes tense, fluid-filled bullae and is most commonly found in adults older than age 60 years. 1 The initial prodromal phase is characterized by mild to intensely pruritic eczematous or urticarial plaques. The condition then progresses to extensive blistering, with formation of tense bullae with or without an erythematous base. Bullae typically last for a few days and commonly are found on the trunk, flexural aspect of extremities, axillae, or inguinal folds; bullae rarely are found on muco- sal surfaces. 2 Differential diagnosis Differentiating between vesicobul- lous diseases is important because prognosis and treatment vary. Classically, vesicobullous diseases were differentiated as positive or negative Nikolsky sign. Positive Nikolsky sign refers to easy separation of the affected epidermis with gentle pressure, while negative Nikolsky sign refers to tense blisters. This sign is negative with bullous pemphigoid, contact dermatitis, linear IgA bullous dermatosis, epider- molysis bullosa acquisita, bullous systemic lupus erythe- matosus, bullous drug eruptions, dermatitis herpetiformis, lichen planus pemphigoides, and porphyria cutanea tarda. The sign is positive with pemphigus vulgaris, Staphylococ- cus-scalded skin syndrome, and toxic epidermal necrolysis. Pemphigoid diseases have varying levels of mucosal involvement. Those that commonly affect the oral mucosa are pemphigus vulgaris, a subtype of epidermolysis bullosa A man with pruritic eruptions Paula Watts; Nasir Aziz, MD; Amor Khachemoune, MD, FAAD, FACMS Paula Watts is a third-year medical student at the Kansas City University of Medicine and Biosciences in Kansas City, Mo. Nasir Aziz is a staff dermatologist at the Veterans Affairs Medical Center in Washington, D.C., and an assistant professor in the dermatology department at Howard University College of Medicine, in Washington, D.C. Amor Khachemoune is program director of the procedural dermatology fellowship at the State University of New York Downstate, a dermatopathologist and Mohs micrographic surgeon at Premier Dermatology in Ashburn, Va., and on the dermatology service at the Veterans Affairs Medical Center and SUNY Downstate Health Sciences Center, both in Brooklyn, N.Y. The author has disclosed no potential conflicts of interest, financial or otherwise. Michael D. Overcash, MPAS, PA-C, department editor DOI: 10.1097/01.JAA.0000466587.18219.2d Copyright © 2015 American Academy of Physician Assistants FIGURE 1. Lesions on the patient’s back Copyright © 2015 American Academy of Physician Assistants