Immunologic dysregulation in a patient with familial hemophagocytic lymphohistiocytosis

A 6‐year‐old Jewish Iranian girl with familial hemophagocytic lymphohistiocytosis (FHLH) is described. The course of the disease fluctuated with partial initial response to antibiotics, steroids, and supportive treatment. Subsequent cytotoxic treatment, including VP‐16, Velban (vinblastine sulfate), and methotrexate (MTX) controlled the disease for a few months but the child died with a clinical picture of meningocephalitis 1.5 years later. Benign‐looking lymphohistiocytic infiltrates with varying degrees of hemophagocytosis were present in the bone marrow, pleural effusion, cerebrospinal fluid (CSF), liver, and brain. Clinical and laboratory evidence of immunologic dysregulation during the disease could be demonstrated. Frequent and intense viral and bacterial infectious diseases were encountered. The laboratory examination most consistently found was the absence of natural killer (NK) cell activity against K562 target cells. The impaired activity of NK cells persisted during all stages of the disease including remission, although NK cell numbers, determined morphologically and immunophenotypically (by Leu‐11, Leu‐7), were normal. Natural killer activity could not be restored by interferon. Moreover, the interferon system appeared to be intact. Impaired monokin interleukin 1 (IL‐I) production by peripheral blood monocytes was found and cound not be restored by indomethacin. Lymphopenia, a mild decrease in T4 numbers, and subsequently, decreased proliferative response to mitogens was noted. Elevated immunoglobulin levels were found during exacerbations and viral episodes, at times accompanied by the presence of auto‐antibodies. The exaggerated fatal lymphohistiocytic response typical for FHLH could be attributed to a underlying genetic pathologic dysregulation of the various immunological response pathways.