Methylenetetrahydrofolate reductase (MTHFR) deficiency is a rare autosomal-recessive inherited disorder; about 100 patients have been reported since its first description in 1972. It is distinct from the common MTHFR gene polymorphism, with mutations that cause mild to moderate reduction in MTHFR activity but no direct clinical manifestations. MTHFR catalyses the reduction of 5,10-MTHF to 5-MTHF, which serves as a methyl donor in the re-methylation of homocysteine to methionine. Biological hallmarks of this disease include hyperhomocysteinaemia, hypomethioninaemia and unusually low folate levels. Clinical symptoms usually start in infancy or childhood. Few adult-onset cases have been described, with psychiatric manifestations, intermittent encephalopathy, polyneuropathy or strokes being reported.1^–5 In all cases, the first manifestations were observed in adolescents or young adults. We now report a woman with MTHFR deficiency, in whom first symptoms occurred in the fifth decade of life.

Case report

A 56-year-old Caucasian woman was referred to our hospital for gait disturbance and acute confusion. Her medical history was remarkable for subdural haematoma in infancy, hysterectomy and surgical intervention for genu valgum, which required knee prosthesis. She was an adopted child, thus no information was available about consanguinity or parents’ medical history. She had one sister and one brother in good health. She worked as a caretaker.

At the age of 51 years, she was admitted to a psychiatric hospital because of severe depression with suicidal attempt. At that time, neurological examination was considered normal. Three years later, a subacute psychotic episode occurred, with visual hallucinations. She was treated …