Interstitial granulomatous dermatitis: A case highlighting possible associations with myeloma and TNF-α inhibitor therapy

Summary: Abstract Body: Interstitial granulomatous dermatitis (IGD) is an uncommon inflammatory skin condition often associated with systemic diseases and drug reactions, including TNF-α inhibitors. We present the case of a 64-year-old female with multiple myeloma undergoing pomalidomide and daratumumab therapy, who developed pruritic erythematous papules on her extremities and trunk. Histopathological examination of punch biopsies revealed interstitial histiocytic inflammation with necrobiosis, confirming the diagnosis of IGD. More recently, IGD is grouped under the umbrella term reactive granulomatous dermatitis with palisaded neutrophilic and granulomatous dermatitis and interstitial granulomatous drug eruption. Laboratory tests were conducted to rule out infectious causes and other systemic conditions, supporting the IGD diagnosis. Given the patient's underlying hematologic malignancy and immunosuppressive therapy, a thorough diagnostic workup was essential. Treatment involved the discontinuation of pomalidomide and daratumumab, after which the patient reported no new lesions, suggesting a possible drug-induced etiology. This case highlights the importance of considering both drug-related and systemic causes in patients presenting with granulomatous dermatitis, particularly those with hematologic malignancies. Comprehensive histopathological evaluation, laboratory data analysis, and clinical correlation are crucial in managing such cases. Further research is needed to elucidate the pathophysiologic mechanisms and optimize management strategies for IGD in this patient population. Zane M. Berry¹, Karan Pandher¹, Mustufa Jafry¹, Marsha Chaffins¹ 1. Henry Ford Health System, Detroit, MI, United States. Adaptive and Auto-Immunity