Novel mutation (E113X) of antithrombin III gene (AT3) in a woman with gestational recurrent thrombosis

A 35-year-old Japanese woman with a low level (42-54%) of blood antithrombin (AT) III, experienced two induced abortions due to deep venous thrombosis at 8 weeks of gestation (GW) and cerebral thrombosis at 10 GW. The present pregnancy was successfully managed with intravenous administration of AT III (6,000-8,000 U/wk). Analysis of polymerase chain reaction (PCR)-single strand conformation polymorphism (SSCP) for exons 3A and 4 of the AT III gene (AT3) using her DNA revealed extra expansion bands with altered migration. The DNA sequencing demonstrated novel mutations in exon 3A of AT3: a G to T substitution at nucleotide position 5333 in codon GAG for Glu 113, causing a stop codon (E113X), and an A to T substitution at position 5338 in codon AAA for Lys 114, forming Asn (K114N). These novel mutations, especially E113X, in AT3 may be related to recurrent thrombosis in the pregnancy.