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.

3型家族性吞噬性淋巴细胞组织细胞增生症（FHL）是由UNC13D基因突变引起的威胁生命的免疫失调综合症，该基因编码munc13–4蛋白，对细胞毒性淋巴细胞的功能很重要。FHL3占FHL病例的30–40％，迄今为止已描述了UNC13D基因中的100多个突变。我们描述的第一例FHL3携带UNC13D的基因内复制，显然是由Alu元素的重组介导的。NK细胞脱粒和munc13–4蛋白表达测定可用于早期识别此类突变，仅通过分析基因组DNA可能会错过这些突变。