Familial hemophagocytic lymphohistiocytosis (FHL) is an autosomal recessive disease of early childhood characterized by nonmalignant accumulation and multivisceral infiltration of activated T lymphocytes and histiocytes (macrophages). Cytotoxic T and natural killer (NK) cell activity is markedly reduced or absent in these patients, and mutations in a lytic granule constituent, perforin, were recently identified in a number of FHL individuals. Here, we report a comprehensive survey of 34 additional patients with FHL for mutations in the coding region of the perforin gene and the relative frequency of perforin mutations in FHL. Perforin mutations were identified in 7 of the 34 families investigated. Six children were homozygous for the mutations, and one patient was a compound heterozygote. Four novel mutations were detected: one nonsense, two missense, and one deletion of one amino acid. In four families, a previously reported mutation at codon 374, causing a premature stop codon, was identified, and, therefore, this is the most common perforin mutation identified so far in FHL patients. We found perforin mutations in 20% of all FHL patients investigated (7/34), with a somewhat higher prevalence, approximately 30% (6/20), in children whose parents originated from Turkey. No other correlation between the type of mutation and the phenotype of the patients was evident from the present study. Our combined results from mutational analysis of 34 families and linkage analysis of a subset of consanguineous families indicate that perforin mutations account for 20%-40% of the FHL cases and the FHL 1 locus on chromosome 9 for approximately 10%, whereas the major part of the FHL cases are caused by mutations in not-yet-identified genes.
Fanconi anemia (FA) is a genetically heterogeneous chromosomal instability syndrome associated with multiple congenital abnormalities, aplastic anemia, and cancer. We report that a deletion mutation in the FANCG gene (c.637_643delTACCGCC) was present in 82% of FA patients in the black populations of Southern Africa. These patients originated from South Africa, Swaziland, Mozambique, and Malawi. The mutation was found on the same haplotype and was present in 1% of controls from the black South African population. These data indicate that the birth incidence of FA in this population is higher than 1 in 40 000, which is much higher than previously supposed, and suggest that the FANCG deletion is an ancient founder mutation in Bantu-speaking populations of sub-Saharan Africa.
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