Maple-syrup-urine disease

**Definition:** Maple syrup urine disease (MSUD) is a disorder of branched-chain amino acids metabolism. Four forms are described. The early onset classic form manifests after birth by lethargy, poor feeding and neurological signs of intoxication. Clinical course without treatment is characterised by deepening coma with maple syrup odour of urine. Subacute MSUD manifests later with encephalopathy, mental disability, major hypotonia, opisthotonus and cerebral atrophy with severe outcome. The intermittent form of MSUD may manifest at any age and presents with repeated ketoacidotic coma. Thiamine-responsive MSUD is a very rare form characterised by improvement of the biochemical profile with thiamine therapy.