Familial hemophagocytic lymphohistiocytosis in two Saudi siblings.

Primary familial hemophagocytic lymphohistiocytosis (HLH; or familial erythrophagocytic lymphohistiocytosis [FEL]) is a heterogeneous autosomal recessive disorder more prevalent with parental consanguinity. There is aggressive proliferation of activated macrophages and histiocytes, which phagocytose red blood cells (RBCs), white blood cells (WBCs), and platelets, leading to anemia, neutropenia and thrombocytopenia. The exaggerated response of immune system in familial HLH can occur in the absence of infection.