Abstract
Summary Molecular analysis has been performed on a patient with coagulation factor XIII A subunit deficiency. A previously published genomic sequence indicates that exon 3 of the factor XIII A subunit gene contains two TaqI restriction sites within which arginine (CGA)→stop (TGA) nonsense mutations are possible. Oligonucleotide primers were therefore used to amplify exon 4 by the polymerase chain reaction. TaqI digestion of the 326 base pair (bp) product derived from normal genomic DNA yielded expected fragments of 244, 73 and 9 bp in size. In the case of the patient, however, an additional fragment of 253 bp was present. Direct sequence analysis showed that the 5′ TaqI site had been lost from one allele by a C→T transition at nucleotide 598. Family studies demonstrated the mutation in the patient's father but no other first‐degree relatives. This is the third independent mutation described in the factor XIII A subunit gene and the first to be identified in a patient compound heterozygous for the disorder.