Maple syrup urine disease in adults12/27/2023 ![]() Prevention of secondary complications: Any trauma care or surgical procedures should be approached in consultation with a metabolic specialist. Consider a trial of enteral thiamine to determine if an affected individual may have thiamine-responsive disease. In those who have not undergone liver transplantation, strict and consistent metabolic control can decrease the risk of developing neuropsychiatric morbidities. Prevention of primary manifestations: Transplantation of allogeneic liver tissue affords affected individuals an unrestricted diet and protects them from metabolic crises, but does not reverse preexisting psychomotor disability or mental illness. Adolescents and adults with MSUD are at increased risk for attention-deficit/hyperactivity disorder, depression, and anxiety disorders and can be treated successfully with standard psychostimulant and antidepressant medications. Brain edema is a common complication of metabolic encephalopathy and requires careful management in an intensive care setting. Some centers use hemodialysis/hemofiltration to remove BCAAs from the extracellular compartment, but this intervention does not alone establish net protein accretion. Acute metabolic decompensation is corrected by treating the precipitating stress while delivering sufficient calories, insulin, free amino acids, isoleucine, and valine to achieve sustained net protein synthesis in tissues. Use of a "sick-day" formula recipe (devoid of leucine and enriched with calories, isoleucine, valine, and BCAA-free amino acids) combined with rapid and frequent amino acid monitoring allows many catabolic illnesses to be managed in the outpatient setting. A BCAA-restricted diet fortified with prescription medical foods can maintain average plasma BCAA concentrations within standard reference intervals and preserves the ratios among them. Treatment of manifestations: Treatment consists of dietary leucine restriction, BCAA-free medical foods, judicious supplementation with isoleucine and valine, and frequent clinical and biochemical monitoring. The diagnosis of MSUD is confirmed by identification of biallelic pathogenic variants in BCKDHA, BCKDHB, or DBT. Follow-up plasma amino acid analysis typically demonstrates elevated concentrations of BCAAs and alloisoleucine. ![]() Suggestive biochemical findings on NBS include whole-blood concentration ratios of (leucine + isoleucine) to alanine and phenylalanine that are above the cutoff values for the particular screening lab. In the era of newborn screening (NBS), the prompt initiation of treatment of asymptomatic infants detected by NBS means that most individuals who would have developed neonatal manifestations of MSUD remain asymptomatic with continued treatment compliance. Individuals with intermediate MSUD have partial branched-chain alpha-ketoacid dehydrogenase deficiency that manifests only intermittently or responds to dietary thiamine therapy these individuals can experience severe metabolic intoxication and encephalopathy in the face of sufficient catabolic stress. Severe intoxication culminates in critical cerebral edema, coma, and central respiratory failure. Worsening encephalopathy manifests as lethargy, apnea, opisthotonos, and reflexive "fencing" or "bicycling" movements as the sweet maple syrup odor becomes apparent in urine Early and nonspecific signs of metabolic intoxication (i.e., irritability, hypersomnolence, anorexia) are accompanied by the presence of branched-chain alpha-ketoacids, acetoacetate, and beta-hydroxybutyrate in urine įour to six days. Elevated concentrations of branched-chain amino acids (BCAAs leucine, isoleucine, and valine) and alloisoleucine, as well as a generalized disturbance of amino acid concentration ratios, are present in blood and the maple syrup odor can be detected in cerumen ![]() Neonates with classic MSUD are born asymptomatic but without treatment follow a predictable course:ġ2–24 hours. Maple syrup urine disease (MSUD) is categorized as classic (severe), intermediate, or intermittent. ![]()
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