CANCER RESEARCH, cilt.59, sa.2, ss.290-293, 1999 (SCI-Expanded)
Heterozygous germ-line mutations in the DNA mismatch repair genes lead to hereditary nonpolyposis colorectal cancer, The disease susceptibility of individuals who constitutionally lack both wild-type alleles is unknown. We have identified three offspring in a hereditary nonpolyposis colorectal cancer family who developed hematological malignancy at a very early age, and at least two of them displayed signs of neurofibromatosis type 1(NF1), DNA sequence analysis and allele-specific amplification in two siblings revealed a homozygous MLH1 mutation (C676T-->Arg226Stop). Thus, a homozygous germ-line MLH1 mutation and consequent mismatch repair deficiency results in a mutator phenotype characterized by leukemia and/or lymphoma associated with neurofibromatosis type 1.