An infant with an extremely rare cobalamin disorder: methionine synthase deficiency and importance of early diagnosis and treatment

摘要

Functional methionine synthase deficiency can be separated into two classes,cobalamin (Cbl) deficiency type E (CblE) and type G (CblG), which are theresult of mutations that affect methionine synthase reductase or methioninesynthase, respectively. Deficiency of methionine synthase activity may resultin megaloblastic anemia without methylmalonic aciduria and neuromuscularabnormality of varying severity. Delayed milestones, ataxia, cerebral atrophy,muscular hypotonia, neonatal seizures, and blindness have been reported asthe associated clinical findings. Early diagnosis and treatment are crucialfor a more favorable diagnosis of the affected cases. Herein we report athree-month-old boy with CblG disease who presented with failure to thrive,chronic diarrhea, feeding intolerance, oral ulcers, microcephaly and hypotonia,and showed a dramatic response to treatment. In the first few months oflife, megaloblastic anemia accompanied by apparent neurological involvementshould direct physicians to order examinations like measurement of totalhomocysteine and methylmalonic acid levels to detect possible forms ofinherited Cbl intracellular metabolism disorders.