Case presentation: A 10.5-year-old girl with a family history of hyperlipidemia and multiple previous operations to remove subcutaneous lipomatous lesions at different parts of her legs, feet and hands, and recent 6.5x5.5 cm right buttock mass near the anus with ulceration. She also had a 1x1 cm left buttock
skin lesion. Her serum triglyceride was 162 mg/dl, cholesterol 811 mg/dl, HDL 226 mg/dl, and LDL 525 mg/dl. The resected left buttock lesion had typical features of a juvenile xanthogranuloma. Right buttock mass had features of a necrobiotic xanthogranuloma characterized by a granulomatous inflammation in the dermis extending into the subcutaneous fat, zones of altered collagen with sheets of histiocytes and inflammatory cells, surrounded by granulomas composed of macrophages with some foreign body-type and Touton giant cells, as well ascholesterol clefts within the necrobiosis. Introduction: Necrobiotic xanthogranuloma (NXG) is a rare, chronic, progressive granulomatous disorder (progressive variant of non-Langerhans cell histiocytosis). Our case had hyperlipidemia and multiple previous operations to remove subcutaneous lipomatous lesions at different parts of her body. This case is presented due to the age, site and large size (6.5 cm) of the lesion, as well as absence of systemic involvement.Discussion: Several hypotheses have been postulated as the exact etiology is not known. It mostly happens in adults and occurance in children is extremely rare. Men and women are affected relatively equally. It manifests as yellowish plaques and nodules. The periorbital area is the commonest site of involvement, but other areas of the face, as well as the trunk and limbs are often involved. Extra-cutaneous involvement is also known. A systemic association in the form of serum monoclonal gammopathy usually of IgG k and λ type is seen in 80% of the adult patients. There is also an increased risk of hematological and lymphoproliferative malignancies. Other less frequent findings include leukopenia, bone marrow plasmacytosis,hypocomplementemia and, occasionally hyperlipidemia. The lesions are yellowish to red-orange papules and nodules that coalesce into indurated plaques, typically 0.5 to 2 cm (rarely up to 7 cm nodules). Lesions often have overlying telangiectasias; scarring and ulceration occur in 40-50% of patients. Histopathologically, NXG is characterized by a granulomatous inflammation in the dermis extending into the subcutaneous fat. There are large zones of necrobiosis (altered collagen with sheets of histiocytes and inflammatory cells) surrounded by granulomas composed of macrophages with some foreign body-type and Touton giant cells. A moderate lymphocytic infiltrate and plasma cells can be seen. Degenerated collagen is common, and mucin deposition can occur. Cholesterol clefts within the necrobiosis are characteristic of NXG.