{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,11,3]],"date-time":"2026-11-03T18:13:24Z","timestamp":1793729604910,"version":"4.6.1"},"reference-count":15,"publisher":"BMJ","issue":"3","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2020,2,4]]},"published-print":{"date-parts":[[2020,3]]},"abstract":"<jats:p>Severe hyperhomocysteinemia (&gt;100 \u00b5mol\/L) is often associated with inborn errors of homocysteine metabolism. It manifests typically in neonatal period with developmental delay, hypotonia, feeding problems or failure to thrive. Adult-onset forms are rare and include less severe manifestations. Early diagnosis is crucial because effective treatment is available. A 23-year-old man presented with a 3-week history of speech and gait impairment, and numbness in lower limbs. Neurological examination revealed dysarthria, decreased vibratory sensation in both legs and appendicular and gait ataxia. Brain MRI revealed T2-hyperintense symmetric white matter lesions and cortical atrophy. He had folate and vitamin B<jats:sub>12<\/jats:sub> deficiency, a markedly elevated serum homocysteine and low methionine. Despite vitamin supplementation homocysteine levels remained elevated. Molecular studies of 5,10-methylenetetrahydrofolate reductase (<jats:italic>MTHFR<\/jats:italic>) gene revealed a new pathogenic mutation (c.1003C&gt;T (p.Arg335Cys)) and a polymorphism (C677T (p.Ala222Val)) associated with hyperhomocysteinemia, both in homozygosity. The patient started betaine with clinical and biochemical improvement.<\/jats:p>","DOI":"10.1136\/bcr-2019-232241","type":"journal-article","created":{"date-parts":[[2020,3,11]],"date-time":"2020-03-11T05:15:14Z","timestamp":1583903714000},"page":"e232241","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":2,"title":["Adult-onset methylenetetrahydrofolate reductase deficiency"],"prefix":"10.1136","volume":"13","author":[{"given":"Daniela","family":"Vieira","sequence":"first","affiliation":[{"name":"Servi\u00e7o de Neurologia, Centro Hospitalar e Universit\u00e1rio de Coimbra EPE, Coimbra, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Cristina","family":"Florindo","sequence":"additional","affiliation":[{"name":"Lab. 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