Clinical and laboratory evaluation of Turkish children with thrombosis for homozygous factor V G1691A mutation.

Factor V (FV) G1691A mutation, in a heterozygous state, is one of the most common inherited risk factors for development of thrombosis. However, the clinical manifestations of homozygosity for the FV G1691A mutation in children is largely unknown because of the limited number of studies reported. The purpose of this study was to evaluate the clinical manifestations and laboratory findings of children with thrombosis who were homozygous for this mutation. Ten patients (four male/six female; mean age, 4.5 years; age range, 1-13 years) who were found to be homozygous for the FV G1691A mutation among 360 consecutive children with thrombosis (2.8%) were the subjects of this study. Six of the 10 patients had venous thrombosis, two had purpura fulminans, one had diffuse skin ecchymosis and one had arterial thrombosis. No history of thrombosis was present in their family members. Seven of the 10 children were under the age of 5 years. One or more additional risk factors (infection, protein S and protein C deficiencies, elevated factor VIII, etc.) were also present in nine of these patients. None of these patients had prothrombin G20210A mutation but one patient had risk-associated plasminogen activator inhibitor-1 gene 4G/4G genotype. These findings suggest that, in the presence of other underlying risk factors, homozygosity for FV G1691A mutation may lead to development of thrombosis at a very young age.