Characterization of a large UNC13D gene duplication in a patient with familial hemophagocytic lymphohistiocytosis type 3

Familial hemophagocytic lymphohistiocytosis (FHL) type 3 is a life-threatening immune dysregulation syndrome caused by mutations in the UNC13D gene, encoding the munc13-4 protein, which is important for function of cytotoxic lymphocytes. FHL3 accounts for 30-40% of FHL cases, and more than 100 mutations in the UNC13D gene have been described to date. We describe the first case of FHL3 carrying an intragenic duplication of UNC13D, apparently mediated by recombination of Alu elements. NK cell degranulation and munc13-4 protein expression assays are useful for early identification of such mutations, which may be missed by analysis of genomic DNA alone.