[Clinical and genetic mutation characteristics of patients with primary hemophagocytic lymphohistiocytosis and their impact on prognosis].

Objective: To investigate the clinical and genetic mutation characteristics of patients with primary hemophagocytic lymphohistiocytosis (HLH) and their impact on prognosis. Methods: Sixty-three primary HLH patients with complete medical records admitted and diagnosed at Beijing Friendship Hospital of Capital Medical University from January 2013 to December 2022 were selected. The patients' clinical and laboratory features, genetic and rapid immunological indicator characteristics, treatment outcomes and prognosis were retrospectively analyzed. Follow-up was up to June 30, 2023, with a median follow-up time [M (Q1, Q3)] of 47 (21, 76) months. Overall survival was analyzed using Kaplan-Meier survival curve, and prognostic factors were analyzed using Cox proportional hazards regression model. Results: Sixty-three primary HLH patients included 35 males and 28 females, with a median age [M (Q1, Q3)] of 17 (7, 27) years. Clinical manifestations at the initial diagnosis mainly included fever (93.7%, 59/63), splenomegaly (87.3%, 55/63), hemophagocytosis (65.1%, 41/63), hepatomegaly (52.4%, 33/63) and central nervous system (CNS) involvement (38.1%, 24/63). A total of 39 patients (61.9%) were diagnosed with EB virus (EBV) infection at initial diagnosis.PRF1 and UNC13D gene mutations were the most common mutations, and the highest frequency mutation site in the PRF1 gene was c.1349C>T, and that of UNC13D gene was c.2588G>A. A total of 76.2% (48/63) of patients had reduced activity of natural killer (NK) cells. Cytotoxic cell degranulation function was impaired or absent in 52.7% (29/55) of patients, of which 79.2% (19/24) of patients with primary HLH with defects in degranulation-related genes had impaired degranulation function. The 1-year and 3-year overall survival rates were 74.8% and 66.7%, respectively. Cox multivariate analysis suggested that peripheral blood EBV≥10 000 copies/ml (HR=3.523, 95%CI: 1.418-8.757, P=0.007) was the risk factor for prognosis. Conclusions: The main clinical manifestations of primary HLH patients at the initial diagnosis include fever, splenomegaly, hemophagocytosis, hepatomegaly, and CNS involvement. PRF1 and UNC13D are the most commonly mutated genes. High copy number EBV infection in peripheral blood is the risk factor for prognosis.