Familial forms of histiocytosis are rare.
FHLH can be caused by mutations in the perforin genes (PRF1 and PRF2), MUNC 13-4 and syntaxin-11.
Faisalabad histiocytosis (MIM.602782) was first described as a novel autosomal recessive form of histiocytosis in a highly consanguineous family originating from Pakistan.