The aim of this study was to elucidate the pathologic sequence changes and associated clinical phenotypes in 9 new patients showing homozygosity for perforin gene among a total of 37 (24%) Turkish FHL families studied by linkage analysis. These 9 unrelated patients (5M/4F) were coming from consanguineous families and their presentation ages of systemic symptoms were ranged from birth to 15 years. Direct sequencing of coding exons of the perforin gene led to the identification of five different homozygous alterations. The nonsense W374X mutation was identified in three patients while four different missense mutations namely G149S, V50M, A91V and novel A523D were detected in the rest six patients. (c) 2007 Elsevier Ltd. All rights reserved.