Description - MSUD is an autosomal recessive disorder characterized by an inability to metabolize the branched chain amino acids, leucine, isoleucine and valine. MSUD is associated with progressive neurological damage beginning within a few days of birth in the severe form. If untreated, most disease forms will result in death within the first day or weeks of life. There is severe metabolic acidosis, usually hypoglycemia, plasma leucine begins to rise usually within 24 hours of birth, and within a few days ketoacids appear in the urine. This results in a characteristic sweet maple syrup odor to the urine, which gives the disease its name. As with virtually all heredity disorders, there are less severe variants, the mildest of which may go undetected for some time until an intercurrent illness unmasks the biochemical abnormalities. It is strongly recommended that any baby suspected of having MSUD be evaluated as quickly as possible.
Clinical Features - Infants with MSUD appear normal at birth, but they usually remain well for only a few days. The affected newborns progress from poor feeding and vomiting to lethargy and coma. A high-pitched cry, irritability, convulsions, spasticity and central nervous system depression are presenting signs.
Treatment - Treatment, which must be continued for life, consists of strict dietary restriction of branched chain aminio acids. Milder variants should have better outcomes with early identification. Normal development and neurologic outcomes have been observed in babies started on treatment prior to developing symptoms. Treatment and diet management by a metabolic consultant is strongly recommended.