Elevated serum ferritin is not specific for hemophagocytic lymphohistiocytosis.

Hemophagocytic lymphohistiocytosis (HLH) is a rare, potentially fatal, syndrome of excessive and ineffective activation of the immune system. The majority of the reported data on HLH is from pediatric patients and lacks specificity. This makes HLH diagnosis challenging especially in adults where HLH is triggered by many conditions and can resemble many disease entities. Elevated ferritin is one of the diagnostic criteria for HLH. We determined the conditions associated with elevated ferritin at our medical center to assess how specific ferritin is for predicting HLH. We retrospectively reviewed all ferritin results >10,000 μg/L in pediatric and adult patients. The most common condition associated with elevated ferritin was hematologic malignancy in adults (25.7%) and HLH in pediatric patients (48.9%). HLH was diagnosed in 14.2% of adults and 48.9% of children with ferritin >10,000 µg/L. Hyperferritinemia occurs in a variety of conditions and is not specific for adult or pediatric HLH. Common causes of elevated ferritin should be considered before entertaining the possibility of HLH, especially in adult patients.