A 50-year-old man presents with a 1-year history of an itchy, bumpy rash on his chest. He denies any history of similar rash and says there have been no “extraordinary changes” in his life that could have triggered this manifestation. Despite consulting various primary care providers, he has been unable to acquire either a definitive diagnosis or effective treatment.
The patient works exclusively in a climate-controlled office. Although there were no changes to laundry detergent, body soap, deodorant, or other products that might have precipitated the rash’s manifestation, he tried alternate products to see what effect they might have. Nothing beneficial came from these experiments. Similarly, the family dogs were temporarily “banished” with no improvement to his condition.
From the outset, the rash and the associated itching have been confined to the patient’s chest. No one else in his family is similarly affected.
The patient is otherwise quite well. He takes no prescription medications and denies any recent foreign travel.
The papulovesicular rash is strikingly uniform. The patient’s entire chest is covered with tiny vesicles, many with clear fluid inside. The lesions average 1.2 to 2 mm in width, and nearly all are quite palpable. Each lesion is slightly erythematous but neither warm nor tender on palpation.
Examination of the rest of the patient’s exposed skin reveals no similar lesions. His back, hands, and genitals are notably free of any such lesions.
A shave biopsy is performed, utilizing a saucerization technique, and the specimen is submitted to pathology for routine processing. The report confirms the papulovesicular nature of the lesions—but more significantly, it shows consistent acantholysis (loss of intracellular connections between keratinocytes), along with focal lymphohistiocytic infiltrates.
What’s the diagnosis?