Case report: Reactive granulomatous dermatitis presenting with inguinal erythematous plaques in a patient administered with pravastatin

An identical group of disorders has been called “interstitial granulomatous dermatitis” and “palisaded neutrophilic and granulomatous dermatitis.” In addition, a drug-induced subset of this condition has been named “interstitial granulomatous drug reaction (IGDR).” More recently, “reactive granulomatous dermatitis (RGD)” has been proposed as an umbrella term encompassing these three disorders. A considerable number of RGD cases are associated with systemic conditions, including autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus, inflammatory bowel disease, and malignancies. IGDR has also been shown to be caused by certain medications. We present a case of a 74-year-old Japanese man showing an asymptomatic, well-demarcated erythema eruption on the bilateral inguinal region extending to the lower abdomen and proximal thigh area. He had hyperlipidemia and had been taking pravastatin for 4 years. A biopsy specimen taken from the erythematous lesion revealed infiltration of lymphocytes and histiocytes in the upper and lower dermis. Interstitial infiltrates of histiocytes and lymphocytes were found as they were dispersed between collagen bundles. Immunostaining showed CD68 + macrophages intermingled with CD4 + and CD8 + T cells. Based on the clinical and histologic findings, the eruption was diagnosed as RGD. Because of the possibility of IGDR, pravastatin was stopped. His eruption completely disappeared within 6 months after the discontinuation. The list of drugs that cause RGD includes angiotensin-converting enzyme inhibitors, antihistamines, β-blockers, antidepressants, anticonvulsants, tocilizumab and ustekinumab. In addition, various statins have been reported to induce drug eruptions. The eruption types are mainly eczematous or lichenoid reactions, with psoriasiform or ichthyosiform reactions occurring rarely. There was only one report documenting that RGD occurred in patients administered rosuvastatin, with annular, violaceous plaques distributed on the extremities, proximal trunk and intertriginous areas. Pravastatin induces lichenoid eruption, but RGD has not been documented. Our case suggests that RGD is underestimated as an adverse effect of statins possibly because of its unusual cutaneous manifestations.