Branded chain ketoacid decarboxylation is defective in
Maple Syrup Urine Disease (MSUD) i. It is also called branched-chain ketonuria. The incidence is 1 per 1 lakh bihs. The name originates from the characteristic smell of urine (similar to burnt sugar or maple sugar) due to excretion of branched-chain keto acids. ii. The basic biochemical defect is deficient decarboxylation of branched-chain keto acids (BKA). iii. Clinical findings: Disease stas in the first week of life. It is characterized by convulsions, severe mental retardation, vomiting, acidosis, coma and death within the first year of life. iv. Laboratory findings: Urine contains branched chain keto acids, valine, leucine, and isoleucine. Rothera&;s test is positive, but unlike in cases of ketoacidosis, even boiled and cooled urine will give the test. Diagnosis depends on enzyme analysis in cells. Diagnosis should be done prior to 1 week after bih. v. Treatment: Giving a diet low in branched chain amino acids. Mild variant is called intermittent branched-chain ketonuria. This will respond to high doses of thiamine. This is because the decarboxylation of the BKA requires thiamine. Liver transplantation has been successfully tried in some cases of MSUD.Ref: DM Vasudevan - Textbook of Biochemistry, 8th edition, page no: 200
Maple syrup urine disease
Hanup disease
Alkaptonuria
GM1 gangliosidosis
Metabolism of lipid