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Case Reports

Abstract

Lipoprotein X is an atypical lipoprotein thought to occur due to reflux of biliary lipoproteins in severe cholestasis and is associated with multiple xanthoma morphologies. We report the case of a 41-year-old gentleman with primary sclerosing cholangitis, hyperlipidemia, and lipoprotein X, who presented with longstanding papulonodular lesions on the extensor surfaces and more recent pruritic, hyperpigmented patches studded with pink-yellow papules on the trunk. Histopathology of a papule revealed cellular, densely packed xanthomatous histiocytes, consistent with a tuberous xanthoma. Biopsy of the patch revealed a loosely dispersed xanthogranulomatous dermal infiltrate. Both specimens showed nuclear pleomorphism, hyperchromasia, and mitotic figures. Immunohistochemistry revealed the lesional cells to be ALK, BRAFV600E, CD1a, langerin, and S100 negative, and CD163 positive. Given the unusual cytology combined with a history of cytopenias, next-generation sequencing was performed to further exclude a neoplastic process, which was negative for pathogenic mutations. We postulate that the pleomorphism is due to degenerative change as opposed to true atypia, with cytology reminiscent of other lesions that may undergo “symplastic” or “ancient” changes (eg, glomus tumors and schwannomas). Furthermore, the mitotic activity may be inherent to the patient’s condition, and previous reports have described mitotic activity in benign xanthogranulomatous entities. Alternatively, some of these cells may represent mitotic-like figures due to degenerative changes, or a harbinger of involution given the concentration in longer-standing lesions. This patient has had a benign clinical course and is being managed symptomatically with topical steroids.