Localization of a gene for familial hemophagocytic lymphohistiocytosis at chromosome 9q21.3-22 by homozygosity mapping

A gene for familial hemophagocytic lymphohistiocytosis (FHL), familial histiocytic reticulosis, and familial erythrophagocytic lymphohistiocytosis, has been localized at chromosome 9q21.3-22 using homozygosity mapping in four inbred families of Pakistani descent. The combined maximum multipoint LOD score was 6.05. Homozygosity across the interval could not be found in another affected kindred, one of Arab origin with a maximum multipoint LOD score of -0.12. Identification of the genes will be helpful to the effort to understand control of macrophage and T-lymphocyte activation. FHL is a rare early-childhood autosomal recessive disorder and involves excessive immune activation.