O/E: there was a wide-spread dermatitis on torso and extremities. No frank bullae but there was a suggestion of vesicles. No burrows were seen. Vesicles were noted on the palms and soles.
An eliptical biopsy was done as well as a 3 mm punch biopsy from perilesional skin for DIF.
Histopath showed: Eosinophilic spongiosis and spongiotic vesiculation.
DIF was positive for IgG in a linear pattern at the DEJ
Histological Photographs courtesy of Dr. Jag Bhawan, Boston University SkinPath Laboratory
Diagnosis: Bullous Pemphigoid secondary to DPP-4 inhibitor.
Discussion: DPP-4 inhibitors are a class of drugs that are used for Type 2 diabetes. There have been eight references to BP as a cutaneous drug effect DPP-4 inhibitors in PubMed (the first was in 2016). It is clear that we will be seeing more of these patients what with the wide-spread usage of DPP-4 inhibitors.
Acknowledgement: Special thanks to Rick Sontheimer, M.D. who alerted me to this phenomenon and Dr. Jag Bhawan for the pathology interpretation and the beautiful photomicrographs.