Familial hemophagocytic lymphohistiocytosis: report of four cases in two families and review of the literature.

Four cases of familial hemophagocytic lymphohistiocytosis (FHL) from two families with first cousins affected in family and siblings in another are presented. The pathological findings, including neuropathology, transmission (TEM), and scanning electron microscopy (SEM), are discussed. This is the first study of this condition to include TEM and SEM. One hundred and fifty-nine cases from the literature, including the author's four cases, are reviewed. The familial occurrence in 116 instances in sibships and consanguinity in 13 of the 73 families support autosomal-recessive inheritance. In five families there were affected first cousins--an observation not readily explained by autosomal-recessive transmission. We suggest that the genetic aspects of FHL be more fully explored and that in future cases parents and other relatives be included in the hematologic, immunologic, and genetic evaluation.