Hemophagocytic lymphohistiocytosis (HLH) is a life-threatening syndrome characterized by pancytopenia and multiple organ infiltrations of lymphocytes and histiocytes with proliferation and hemohpagocytic activity. HLH is classified as primary (or familial) and secondary. Familial HLH is common in infants and young children, and is related to genetic defects. This article aims to review research advances on PRF1, UNC13D, STX11 and STXBP2, as well as the other 5 genes associated with familial HLH based on molecular genetics, and to summarize diagnosis and treatment methods for this disease.