Detection of 598C>T mutation. Sequencing of exon 3 of the VHL gene detected a homozygous base change of C to T at nucleotide 598 in patients A1 to A3, B1 to B3, and C1 (A) when compared with the normal sequence (B). One patient, D1, was heterozygous for this base change (C). The position of the mutation is indicated by an arrow. The 598C>T mutation destroys the restriction site for BsrBI enzyme and the normal exon 3 PCR product is restricted into 2 fragments of 330 and 132 bp, but in the presence of the 598C>T mutation only a 462-bp fragment is obtained. Screening of family members of C1 indicated that his mother was heterozygous and his sibling was normal (D). The father of D1 is normal but his mother and son are heterozygous for the 598C>T (E). M indicates 100-bp DNA ladder; MC1, mother of patient C1; C1, patient C1; SC1, sibling of C1; FD1, father of patient D1; MD1, mother of patient D1; D1, patient D1; and SD1, son of D1.