Reactive granulomatous dermatitis as a paraneoplastic phenomenon.

Reactive granulomatous dermatitis (RGD) represents a broad group of cutaneous inflammatory skin conditions including interstitial granulomatous dermatitis (IGD), palisaded neutrophilic and granulomatous dermatitis (PNGD), and interstitial granulomatous drug reaction (IGDR). These conditions are frequently associated with autoimmune disorders and secondary to medications. They can also present as paraneoplastic syndromes. RGD usually presents as erythematous papules, plaques, or nodules, distributed symmetrically, especially on the inner aspect of the arms and thighs, the flank of the trunk, the lower part of the abdomen, and intertriginous areas like the axilla. Histologically, IGD classically reveals interstitial histiocyte and lymphocyte infiltration, plus multinucleated giant cells. As a paraneoplastic disease, IGD may occur in myelodysplastic syndromes, leukemias, and such solid tumors found in the breast and lungs. The successful diagnosis of IGD relies on both histopathologic examination and clinical evaluation. Although administration of corticosteroids can offer symptomatic relief of the skin lesions, treatment requires addressing the underlying condition when identified. Awareness of RGD's potential as an early marker for systemic disease, especially malignancy, is important for diagnostic and interventional purposes.