Aims: To characterize the clinical, demographic, laboratory, and molecular biologic findings in children with HLH diagnosed and treated in our center.
Background: Hemophagocytic lymphohistiocytosis (HLH) is a rare immuno-hematologic disorder more common in children than adults. It is divided into two separate conditions which are not always easy to differentiate: familial/primary HLH (FHL) and acquired/secondary HLH associated with malignant, infectious, and other inflammatory conditions. FHL is a life-threatening disorder caused mainly by mutations in genes that code for proteins participating in perforin-dependent cell death.
Methods: We collected data from the records of all children who were diagnosed with HLH according to the accepted HLH criteria, and treated in the Schneider Children's Medical Center of Israel between the years 2004-2020. Demographic, clinical and laboratory data were summarized into a national database.
Results: A total of 36 children (18 boys,18 girls) who were diagnosed as having HLH according to the diagnostic criteria and received treatment according to the Histiocyte Society '94 or 2004 international protocols, entered the study. Eleven of the patients were Arab (30%), while 25 were Jewish (70%). The most frequent clinical signs were fever (89%) and hepatosplenomegaly (61%). Laboratory tests showed bipenia in 100% and increased levels of Interleukin-2 receptor (IL-2R) in 97%. Mutations in 3 out of the 4 common HLH genes were found in 15 (42%) children. The most common mutant gene was MUNC 13-4 comprising 40% of mutant genes. Mutations were quite common among Arab patients (81%) compared to the Jewish HLH population (20%) (p<0.001). Patients bi-allelic MUNC 13-4 mutations had a particularly poor prognosis with 66% succumbing to the disease.
Conclusions: HLH is a severe, multisystem disorder. High clinical suspicion leading to timely diagnosis and treatment are crucial for preventing poor outcome and death. Genetic studies are of upmost importance in our population due to the high percentage of mutations, especially in the Arab population.