Interstitial Granulomatous Drug Reaction: A Case Report.

Interstitial granulomatous drug reaction (IGDR) is a rare inflammatory reaction of the skin with an unknown etiology. Here, we report the case of a 55-year-old female with a history of diabetes mellitus and hypertension who presented with an asymptomatic persistent skin lesion over the left breast for more than one year. Skin examination revealed a single non-scaly, sharply demarcated, erythematous annular patch. Skin biopsy showed epidermal atrophy and histiocytic infiltrate throughout the entire dermis, both interstitial and perivascular. The patient was diagnosed with IGDR. We decided not to change her medications because her chronic diseases were well-controlled on these medications; her skin lesion was asymptomatic, very mild, and localized to a small body area; and, lastly, IGDR is not associated with any complications in the future.