Type I Gaucher disease due to homozygosity for the 259T mutation in a Bedouin patient.

A 26-year-old Bedouin with moderate thrombocytopenia and enlarged spleen and liver was diagnosed as having type I Gaucher disease based on the presence of Gaucher cells in the bone marrow biopsy and enzymatic determination of glucocerebrosidase activity. Molecular analysis excluded 10 common mutations in the glucocerebrosidase gene. Homozygosity for the C --> T mutation in nucleotide 259 of the cDNA (1763 genomic) was detected by digestion with restriction enzyme StyI after an amplification of a portion of exon 3 by mismatched primers. This is the first known case of homozygosity for this mutation. The fact that it produces a very mild phenotype, confirms a previous suggestion that 259T can be classified as a "mild" mutation. Association of the 259T mutation with the "Pv 1.1 +" haplotype is consistent with a common origin of the mutated alleles.