COEXISTENCE OF HEREDITARY HOMOCYSTINURIA AND FACTOR-V LEIDEN - EFFECTON THROMBOSIS

Background. Venous and arterial thromboembolism occurs in only about o ne third of patients homozygous for homocystinuria, which suggests tha t other, contributory factors are necessary for the development of thr ombosis in these patients, Factor V Leiden, an R506Q mutation in the g ene coding for factor V, is the most common cause of familial thrombos is and could be a potentiating factor. Methods. We determined activate d partial-thromboplastin times in the presence and absence of activate d protein C and tested for the factor V Leiden mutation in 45 members of seven unrelated consanguineous kindreds in which at least 1 member was homozygous for homocystinuria. Results. Thrombosis (venous, arteri al, or both) occurred in 6 of 11 patients with homocystinuria (age, 0. 2 to 8 years), All six also had the factor V Leiden mutation. One pati ent with prenatally diagnosed homocystinuria who was also heterozygous for factor V Leiden has received warfarin therapy since birth and has not had thrombosis (age, 18 months), Of four patients with homocystin uria who did not have factor V Leiden, none had thrombosis (ages at th is writing, 1 to 17 years). Three women who were heterozygous for both homocystinuria and factor V Leiden had recurrent fetal loss and place ntal infarctions. Conclusions. Patients with concurrent homocystinuria and factor V Leiden can have an increased risk of thrombosis, Screeni ng for factor V Leiden may be indicated in patients with homocystinuri a and their family members. (C) 1996, Massachusetts Medical Society.