• Kozo Nagai, Ken Yamamoto, Hiroshi Fujiwara, Jun An, Toshiki Ochi, Koichiro Suemori, Takahiro Yasumi, Hisamichi Tauchi, Katsuyoshi Koh, Maho Sato, Akira Morimoto, Toshio Heike, Eiichi Ishii, and Masaki Yasukawa.
• Department of Bioregulatory Medicine, Ehime University Graduate School of Medicine, Ehime, Japan.
• Plos One. 2010 Jan 1;5(11):e14173.

BackgroundFamilial hemophagocytic lymphohistiocytosis (FHL) is a rare disease of infancy or early childhood. To clarify the incidence and subtypes of FHL in Japan, we performed genetic and functional analyses of cytotoxic T lymphocytes (CTLs) in Japanese patients with FHL.Design And MethodsAmong the Japanese children with hemophagocytic lymphohistiocytosis (HLH) registered at our laboratory, those with more than one of the following findings were eligible for study entry under a diagnosis of FHL: positive for known genetic mutations, a family history of HLH, and impaired CTL-mediated cytotoxicity. Mutations of the newly identified causative gene for FHL5, STXBP2, and the cytotoxicity and degranulation activity of CTLs in FHL patients, were analyzed.ResultsAmong 31 FHL patients who satisfied the above criteria, PRF1 mutation was detected in 17 (FHL2) and UNC13D mutation was in 10 (FHL3). In 2 other patients, 3 novel mutations of STXBP2 gene were confirmed (FHL5). Finally, the remaining 2 were classified as having FHL with unknown genetic mutations. In all FHL patients, CTL-mediated cytotoxicity was low or deficient, and degranulation activity was also low or absent except FHL2 patients. In 2 patients with unknown genetic mutations, the cytotoxicity and degranulation activity of CTLs appeared to be deficient in one patient and moderately impaired in the other.ConclusionsFHL can be diagnosed and classified on the basis of CTL-mediated cytotoxicity, degranulation activity, and genetic analysis. Based on the data obtained from functional analysis of CTLs, other unknown gene(s) responsible for FHL remain to be identified.

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