A 38-Year-Old Dog Owner With a Blistering, Itchy Rash

Melba Estrella, MD; Alan Snyder; John Plante; Dirk M. Elston, MD


October 29, 2020

Editor's Note:
The Case Challenge series includes difficult-to-diagnose conditions, some of which are not frequently encountered by most clinicians but are nonetheless important to accurately recognize. Test your diagnostic and treatment skills using the following patient scenario and corresponding questions. If you have a case that you would like to suggest for a future Case Challenge, please contact us .


A 38-year-old man presents with a relapsing pruritic rash of 3 years' duration on his buttocks. He has no significant past medical history. Initially, he noticed several small, itchy, red bumps on his upper buttocks that increased in number and size concurrently with the appearance of blisters. The blisters tended to break open after scratching.

The rash first appeared after the patient adopted a dog from a shelter. He suspected that he might have contracted an infection from the dog and self-treated with an over-the-counter topical antimicrobial ointment, with no improvement. He later sought medical attention from his primary care provider, who prescribed a topical corticosteroid cream. Although multiple applications of the topical corticosteroid resulted in improvement, flares would arise when the cream was discontinued.

The patient states that the rash seems to be progressively worsening, mainly during warm weather, but he cannot identify specific triggers. He denies further dissemination of the lesions but recalls having had a similar milder version of the rash on both of his ankles, which subsided after he switched from ankle-cut socks to extra–low-cut socks.

The patient has no other rashes. He denies pain and recent fever or chills, travel, infections, and changes in weight. He is an otherwise healthy radiology technician who lives with his wife and dog. He has not been exposed to a family member or other contact with a similar rash. He changes daily into a clean uniform provided by his workplace and denies the use of new or borrowed clothing. The patient has no known medical allergies and is not taking medication. His immunizations are up to date.


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