Aim To examine the status of blood coagulation factors in patients with mucopolysaccharidosis (MPS) type II. To diagnose of polymorphism in the genes of coagulation in this pathology.

Materials and methods We observed 16 boys with MPS II type. The deficiency of XII factor (Hageman factor) was detected in half of patients; meanwhile we found the combined deficiency of XII factor with deficiency of other factors of blood coagulation: two patients had combined deficiency of IX and VIII factors; one patient had deficiency of VII and VIII factors; a single case – the deficiency of IX factor. One patient had a deficiency of VIII, VII, IX factors. However, the deficiency of von Willebrand factor (VWF) was found only in 1 case, but without the deficiency of XII factor.

We found polymorphisms in genes of coagulation. It was discovered carriage of modified alleles in the genes encoding the enzymes involved in homocysteine metabolism: MTHFR (methylentetrahydrofolate) and MTRR (methionine-synthase-reductase) and plasminogen activator inhibitor PLANH1 5G.

The gene polymorphism of ???FR found almost half of the cases. The heterozygous state of MTHFR C677C/T gene identified in 37.5% of cases; homozygous state C667 T/T in 12%. Heterozygous carriers of the MTRR A66G met at −56,25% of the patients, and homozygous MTRR G66G – 31,25% of patients. The polymorphism −675 4G/5G (5G->4G) of plasminogen activator inhibitor PLANH1 5G (−675)4G was found in 31% patients.

Discussion The results of the study suggest that in children with MPS high probability of a deficiency of Hageman factor, not only in isolation but also in combination with a deficiency of certain other blood coagulation factors. The presence of polymorphisms in genes of coagulation responsible for the exchange of the folate cycle and methionine can play the role of trigger factors in the development of thrombosis, thromboembolism, especially in combination with a deficiency of the Hageman factor.

Conclusion The investigation of these parameters plays a prognostic role in the development of possible complications of the hemostatic system in children with chronic diseases of the cardiovascular system.