Case report: Onychopapilloma in a patient with BAP1 tumor predisposition syndrome—a useful clinical marker?

The BAP1 gene encodes a tumor suppressor protein implicated in BAP1 tumor predisposition syndrome (BAP1-TPDS), a hereditary condition associated with an increased risk of uveal and skin melanoma, mesothelioma, and renal cancer. In this case report, we describe a male patient diagnosed with mesothelioma carrying a germline BAP1 variant. The patient exhibited severe nail abnormalities affecting all ten fingernails and several toenails. To our knowledge, the association between onychopapilloma and pathogenic germline BAP1 variants has only been reported once in the literature. The patient had experienced nail abnormalities since adolescence. Based on these findings, we propose that polydactylous onychopapilloma may serve as a clinical marker of BAP1-TPDS in otherwise asymptomatic individuals, and could potentially aid in early identification of at-risk carriers.