Abstract
BACKGROUND: Methylenetetrahydrofolate reductase (MTHFR) deficiency is a rare inborn error of metabolism inherited in autosomal recessive pattern and is associated with a wide spectrum of neurological abnormalities. CASE PRESENTATION: We herein describe a 15-year-old boy with MTHFR deficiency who presented with a slowly progressive decline of school performance and a spastic gait. Rapidly deteriorating psychosis and repetitive seizures triggered by a febrile infection prompted neurological investigation. He had significantly elevated total plasma homocysteine and urinary homocystine levels, as well as a decreased plasma methionine level. Brain magnetic resonance imaging (MRI) revealed leukoencephalopathy. DNA gene sequencing showed c.446_447 del GC ins TT and c.137G > A, and c.665C > T heterozygous mutations in the MTHFR gene of the patient. Oral administration of betaine drastically improved his clinical symptoms within a few months. After 8 months of treatment, his total plasma homocysteine level moderately decreased; and the plasma methionine concentration became normalized. Furthermore, the white matter lesions on MRI had disappeared. CONCLUSION: This patient demonstrates the possibility that MTHFR deficiency should be considered in mentally retarded adolescents who display an abnormally elevated plasma level of homocysteine in association with progressive neurological dysfunction and leukoencephalopathy. Febrile infections may be an aggravating factor in patients with MTHFR deficiency.