Review of diagnosis and treatment practices of pediatric and adult hemophagocytic syndromes

Hemophagocytic syndromes (HFSs) are rare, life-threatening conditions characterized by hypercytocinemia, systemic inflammation, and overstimulation of the immune system leading to multi-organ failure. Primary Hemophagocytic Lymphohistiocytosis (HLH) is caused by genetic mutations that impair the cytotoxic function of natural killer (NK) and cytotoxic T cells and is typically found in infancy and childhood. Primary HLH includes familial HLH (aHLH), in which patients have autosomal recessive mutations in Perforin. Secondary hemophagocytic syndromes usually affect adolescents and adults and are not associated with known genetic defects, with rare cases of aHLH over 70 years of age reported. Diagnostic criteria specific to adult HPS have not been established and diagnosis is largely based on the Histiocyte Society's HLH-94 or 2004 pediatric diagnostic criteria. As with diagnosis, treatment protocols for adult HPS/HLH are usually estimated from pediatric HLH-94 and HLH-2004 protocols. How well these treatment protocols apply to adults is not fully understood. Existing literature on HPS/HLH has significant clinical and methodological heterogeneity. Therefore, it is planned to review the diagnostic criteria and treatment practices of hemophagocytic syndromes (HFSs), including both pediatric and adult Hemophagocytic lymphohistiocytosis (HLH), in the light of the literature.