[Severe hyperhomocysteinemia revealing homocystinuria in two young adults with mild phenotype].

Introduction: To the request of total plasma homocysteine determination in the investigation of vascular disease, diagnosis of homocystinuria in young adult patients with mild phenotype is not so rare.

Exegesis: A 26-year-old man developed embolic cerebral infarction and a 22-year-old woman presented a right renal venous thrombosis one week after delivery. In each case, high concentration of total plasma homocysteine was first found and plasma and urinary amino acids analysis later on directed the diagnosis towards homocystinuria. Finally, reduced skin fibroblast cystathionine beta-synthase activity confirmed the diagnosis of homocystinuria.

Conclusion: Total plasma homocysteine determination must be determined for screening for hyperhomocysteinemia in young adults with venous thromboembolism without characteristic phenotypic features of homocystinuria.