Hemophagocytic lymphohistiocytosis (HLH) is polygenetic disease caused by mutations in genes associated with granule-dependent lymphocyte-mediated cytotoxicity (PRF1, UNC13D, STX11, STXBP2, LYST, AP3B1, AP3D1 RAB27A, XIAP, SH2D1A).

Our cohort of patients demonstrated a repeated mutation in the UNC13D genec.2346_2349delCTCC(p.R782fs), which may be associated with the “founder effect” in Slavic countries. Atypical manifestation causes difficulties in rapid diagnosis, fast sequencing of all PID genes are necessary for establishing correct diagnosis and start appropriate treatment.