An encephalitis-like syndrome in an adult with methylmalonic acidemia and hyperhomocysteinemia: A case report.
Rongjin Zhang, Xiaona Sheng
✦ AI-curated · Sources linked
Case in brief
A 56-year-old man developed fever and slowed responses, followed by disorganized speech, visual hallucinations, impaired consciousness, and pyramidal signs. Evaluation showed total homocysteine > 100 µmol/L, elevated propionylcarnitine and C3/acetylcarnitine ratio, and increased urinary methylmalonic acid and methylcitrate, supporting methylmalonic acidemia with hyperhomocysteinemia on biochemical grounds. Glutamic acid decarboxylase 65 antibodies were positive in serum and CSF, but other findings did not establish autoimmune encephalitis. He improved during concurrent metabolic, immunologic, anti-infective, and supportive treatments; no single treatment could be credited. No recurrence was reported at 6-month follow-up.
What made this case unusual
The encephalitis-like presentation and positive glutamic acid decarboxylase 65 antibodies complicated recognition of a biochemically supported metabolic disorder in an adult.
Diagnostic / clinical pearl
In an adult with an encephalitis-like syndrome, marked hyperhomocysteinemia and pyramidal signs should prompt metabolic screening; interpret antibody positivity alongside biochemical, imaging, and CSF findings rather than in isolation.