Adverse outcomes in primary hemophagocytic lymphohistiocytosis

Hemophagocytic lymphohistiocytosis (HLH) is a rare condition characterized by abnormal proliferation of macrophages. Although the mortality rate in children diagnosed with primary HLH is high, little has been described about the nature of adverse events. This review evaluates unfavorable events in children with primary HLH to suggest methods of improving outcomes.

Charts of patients who met diagnostic criteria for primary HLH at the Hospital for Sick Children between January 1985 and June 2000 were retrospectively reviewed. The primary outcome measure was an adverse event, defined as death, the subsequent diagnosis of malignancy, or developmental delay.

Twenty children were diagnosed with primary HLH. The median age at diagnosis was 6.5 months (range 1-78 months). Nineteen children received chemotherapy and two underwent matched sibling donor bone marrow transplantation. Of the 20 children, 12 (60%) died. These deaths were attributed to progressive HLH in 4 cases and invasive infection in 8 cases. These infections consisted of disseminated cytomegalovirus infection (n = 1), sepsis (n = 1), and invasive fungal infections (n = 6). Eight children survived. Two were subsequently diagnosed with malignancy. Two others were found to have significant developmental delay.

The overall mortality rate was 60% in our series of 20 children with primary HLH; 50% of deaths were directly attributable to invasive fungal infection. Developmental delay and the diagnosis of malignancy are important events in this cohort.