Necrobiotic xanthogranuloma

Necrobiotic xanthogranuloma (NXG) is a rare chronic progressive non-Langerhans cell histiocytic disorder characterized by destructive skin lesions that most commonly appear as indurated yellowish-orange to reddish-brown papules, nodules, and plaques. These lesions predominantly affect the periorbital region (around the eyes) but can also occur on the trunk, extremities, and other areas of the body. Histologically, the lesions show granulomatous inflammation with zones of necrobiosis (tissue degeneration), cholesterol clefts, foreign body giant cells, and Touton giant cells. A hallmark association of NXG is the presence of a monoclonal gammopathy, most commonly IgG kappa, which is found in the vast majority of patients. Some patients may progress to develop lymphoproliferative disorders, including multiple myeloma. The disease primarily affects the skin and eyes, but systemic involvement can occur, affecting internal organs such as the lungs, heart, kidneys, liver, spleen, and muscles. Ocular complications are common and can include ulcerative keratitis, uveitis, proptosis, and orbital masses, which may threaten vision. Patients may also experience elevated erythrocyte sedimentation rate, leukopenia, and cryoglobulinemia. The disease typically presents in middle-aged to older adults, with a mean age of onset around 60 years. Treatment of necrobiotic xanthogranuloma remains challenging, and no universally effective therapy has been established. Management strategies include surgical excision of lesions, systemic corticosteroids, alkylating agents (such as chlorambucil or melphalan), intravenous immunoglobulin (IVIG), and plasmapheresis. More recently, targeted therapies directed at the underlying paraproteinemia, including lenalidomide and rituximab, have shown promise in some patients. Treatment of the associated hematologic condition, when present, may also lead to improvement of skin lesions. Given the chronic and relapsing nature of the disease, long-term follow-up and monitoring for progression to hematologic malignancy are essential.

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