Without the needed enzyme, known as branched-chain ketoacid dehydrogenase (BCKAD), these amino acids and their byproducts accumulate and cause damage to the body. These amino acids are found in all foods containing protein. MSUD is caused by the lack of an enzyme needed to break down three amino acids: leucine, isoleucine, and valine, which are collectively known as the branched-chain amino acids. If carefully treated with a low-protein diet, people with MSUD can live fairly normal lives. Maple syrup urine disease (MSUD) type 1B is an inherited metabolic disorder named for the characteristic maple syrup smell of the affected person’s urine. Effective management of the complex pathophysiology of this biochemical disorder requires integrated management of general medical care and nutrition, as well as control of several variables that influence endogenous protein anabolism and catabolism, plasma amino acid concentrations, and serum osmolarity.What is Maple Syrup Urine Disease Type 1B?
However, neurologic function may deteriorate rapidly at any age because of metabolic intoxication provoked by common infections and injuries. These 4 patients each showed evidence that acutely decreased serum sodium concentration and decreased serum osmolarity were associated with rapid progression of cerebral edema during their acute illnesses.Ĭlassical MSD can be managed to allow a benign neonatal course, normal growth and development, and low hospitalization rates. Four patients developed life-threatening cerebral edema as a consequence of metabolic intoxication induced by infection, but all recovered. In all infants, plasma leucine levels decreased to 219 patient years showed that, although common infections frequently cause loss of metabolic control, the overall rate of hospitalization after the neonatal period was only 0.56 days per patient per year of follow-up, and developmental outcomes were uniformly good. 2) Using our treatment protocol, 18 additional infants who were biochemically intoxicated at the time of diagnosis recovered rapidly. None of the infants identified before 3 days of age and managed by our treatment protocol became ill during the neonatal period, and 16 of the 18 were managed without hospitalization. The molar ratio of leucine to alanine in plasma ranged from 1.3 to 12.4, compared with a control range of 0.12 to 0.53. Branched-chain ketoacid excretion was monitored frequently at home and branched-chain amino acid levels were measured within the time of a routine clinic visit, allowing immediate diagnosis and treatment of metabolic derangements.ġ) Eighteen neonates with MSD were identified in the high-risk group (n = 39) between 12 and 24 hours of age using amino acid analysis of plasma or whole blood collected on filter paper.
Similar principles were followed for both sick and well outpatient management, especially during the first year, when careful matching of branched-chain amino acid intake with rapidly changing growth rates was necessary. The treatment protocol for acute illnesses included the use of mannitol, furosemide, and hypertonic saline to maintain or reestablish normal serum sodium and extracellular osmolarity and thereby prevent or reverse life-threatening cerebral edema. During acute illnesses, the rate of decrease of the plasma leucine level was monitored as an index of net protein synthesis. Our protocol emphasizes the enhancement of protein anabolism and dietary correction of imbalances in plasma amino acids rather than removal of leucine by dialysis or hemofiltration. A treatment protocol for MSD was designed to 1) inhibit endogenous protein catabolism, 2) sustain protein synthesis, 3) prevent deficiencies of essential amino acids, and 4) maintain normal serum osmolarity. An additional 18 infants with MSD were diagnosed between 4 and 16 days of age because of metabolic illness. Amino acid concentrations were measured in blood specimens from these at-risk infants between 12 and 24 hours of age. To evaluate an approach to the diagnosis and treatment of maple syrup disease (MSD).įamily histories and molecular testing for the Y393N mutation of the E1alpha subunit of the branched-chain alpha-ketoacid dehydrogenase allow us to identify infants who were at high risk for MSD.
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