What could be causing this man’s blisters?

A 75-year-old man presented with a sudden onset of blisters on his anterior proximal thighs (Figure 1) and on his left arm (Figures 2 and 3) but not on his right arm. He had undergone a hernia repair 1 week ago from which he had been recovering uneventfully until now. The lesions on his thighs were asymptomatic, but the ones on his left arm were tender. The blisters appeared to follow the dermatome on the arm. He was otherwise healthy and was not taking any new medications.

What could be causing this man’s blisters?

A. Contact dermatitis
B. Delayed drug reaction to medication(s) for thehernia repair
C. Bullous impetigo
D. Herpes zoster
E. Bullous pemphigoid

Answer on next page

Answer: Contact dermatitis and herpes zoster

This patient acquired herpes zoster (shingles) on his left arm at the same time as having developed contact dermatitis on his thighs, most likely due to surgical preparation at the time of his hernia repair. The contact dermatitis should have been pruritic, but he denied having any symptoms. He was placed on antiviral therapy for the shingles and a short prednisone taper for the contact dermatitis; both problems resolved uneventfully.

A delayed drug reaction would be expected to be more widespread and pruritic. Bullous impetigo is a concern, but again one would expect more crusting and fewer intact blisters on the man’s arm. Bullous pemphigoid is very pruritic, but the only symptom reported here was tenderness.