Molecular spectrum of genetic causes of HLH includes; FHL1 with unknown gene defect, FHL2 caused by PRF1 gene defect, FHL3 caused by UNC13D gene defect, FHL4 caused by STX11 gene defect, FHL5 caused by STXB2 gene defect, Chediak-Higashi syndrome caused by LYST gene defect, Hermansky-Pudlak caused by AP3B1 gene defect, Griscelli syndrome type 2 caused by RAB27A gene defect, X-linked proliferative type 1 caused by SHD2D1A gene defect and X-linked proliferative type 2 caused by BIRC4 gene defect [3]. The gene discussed is STX11; the disease is Chédiak-Higashi syndrome.