Homozygous W374X mutation was identified in unrelated 13 patients (6M/7F) from consanguineous families, 62% of which had history of deceased sibling. Haplotype analysis provided evidence for the probable existence of a founder effect. Age at disease onset ranged from 1 day to 5.5 months (median 2 months). Hepatic dysfunction was observed in 69%, ascite 62%, hypertriglyceridemia 77%, each hyperferritinemia and hypofibrinogenemia 85%, CNS involvement 46% of patients while birth weights were in normal range. Those with very high ferritin (>20,000. ng/ml) had extremely low fibrinogen levels. Two-thirds of patients receiving HLH protocol died within 20 days of therapy. © 2010 Elsevier Ltd.