Antithrombin Krakow II (c.624+1 G > T): a novel mutation leading to type 1 antithrombin deficiency

Hereditary antithrombin (AT) deficiency is a rare autosomal disease. More than 200 mutations have been described in the AT gene leading to its deficiency. We describe here a case of type I AT deficiency in a 26-year-old Polish man who experienced proximal deep vein thrombosis and pulmonary embolism associated with a transient thrombotic risk factor, the right ankle trauma, despite the use of low-molecular-weight heparin prophylaxis. The family history was negative for venous thromboembolism. The AT activity was initially 47% and on repeated analysis 53%, and the antigen level, 0.15 g/l. The analysis of AT gene revealed the presence at the heterozygous state of a substitution G more than T located at the first nucleotide 3' of exon 3a (c.624 + 1 G > T, Human Genome Variation Society numbering system). The substitution might be detrimental taking account for its position in a donor splice site. To the best of our knowledge this mutation has not been previously described, so it was named antithrombin Krakow II.