Background: Hemophagocytic lymphohistiocytosis (HLH) is a rare but severe, life-threatening inflammatory condition if untreated. We aimed to investigate the etiologies, outcomes, and risk factors for death in children and adults with HLH. Methods: The medical records of patients who met the HLH criteria of two regional university hospitals in Korea between January 2001 and December 2019 were retrospectively investigated. Results: Sixty patients with HLH (35 children and 25 adults) were included. The median age at diagnosis was 7.0 years (range, 0.1-83 years), and the median follow-up duration was 8.5 months (range, 0-204 months). Four patients had primary HLH, 48 patients had secondary HLH (20 infection-associated, 18 neoplasm-associated, and 10 autoimmune-associated HLH), and eight patients had HLH of unknown cause. Infection was the most common cause in children (14/35, 40.0%), whereas neoplasia was the most common cause in adults (13/25, 52.0%). Twenty-eight patients were treated with HLH-2004/94 immunochemotherapy. The 5-year overall survival (OS) rate for all HLH patients was 59.9%. The 5-year OS rates for patients with primary, infection-associated, neoplasm-associated, autoimmune-associated, and unknown cause HLH were 25.0%, 85.0%, 26.7%, 87.5%, and 62.5%, respectively. Using multivariate analysis, neoplasm-induced HLH (p = 0.001) and a platelet count < 50 × 10 9 /L (p = 0.008) were identified as independent risk factors for poor prognosis in patients with HLH. Conclusion: Infection was the most common cause of HLH in children, while it was neoplasia in adults. The 5-year OS rate for all HLH patients was 59.9%. HLH caused by an underlying neoplasm or a low platelet count at the time of diagnosis were risk factors for poor prognosis.

Severe skin reactions complicating tumor necrosis factor-alpha (TNF-α) antagonist therapy were somewhat reported in adults. We report a case of 24-month-old boy with refractory Kawasaki disease who developed toxic epidermal necrolysis (TEN) after one dose of 5mg/kg infliximab. The patient responded to intravenous hydrocortisone and was able to discharge without any other serious complications. The clinicians should be aware of the potential for severe skin reactions from the use of TNF-α antagonists in children.