HLH appears to affect all ages, although the hereditary and sporadic cases are reported primarily in children; a crude annual incidence of 1.2 cases of familial hemophagocytic lymphohistiocytosis per million children has been reported in Sweden. Large series of HLH cases have been reported in Hong Kong[18,31] and Taiwan[12,32], but whether the incidence of HLH is higher in Asia than in Europe or North America is not known. A seasonal pattern has been suggested in which cases may occur more often in the summer.
The familial form of HLH occurs in young children as a genetic disorder with autosomal recessive inheritance; possible loci for a responsible gene or genes have recently been mapped to the long arms of chromosomes 9 and 10. HLH may also occur as a complication of Chediak-Higashi syndrome or after EBV infection in patients with X-linked lymphoproliferative syndrome. In these patients, fatal infectious mononucleosis may be pathologically indistinguishable from HLH.
In 1979, HLH was described in a cohort of patients who had serologic evidence of recent viral infections, and virus-associated hemophagocytic syndrome was proposed as a distinct clinical entity. Subsequently, HLH has been reported in association with a variety of infections, and the term reactive hemophagocytic syndrome has been suggested to distinguish HLH associated with an identifiable infectious or noninfectious etiology from its hereditary forms. However, the reactive and hereditary forms of the disease are difficult to distinguish; for example, patients with familial forms of HLH may have hemophagocytic syndrome after a documented viral infection.
Emerging Infectious Diseases. 2000;6(6) © 2000 Centers for Disease Control and Prevention (CDC)
Cite this: Hemophagocytic Syndromes and Infection - Medscape - Nov 01, 2000.