Maple syrup urine disease (MSUD)
an autosomal recessive metabolic disorder due to deficiency of the mitochondrial branched-chain alpha-keto acid dehydrogenase (BCKD)
The body is unable to break down certain branched chain amino acids (BCAA) causing elevated blood levels of BCKD and increased urinary excretion of BCAA -> sweet smelling urine
Typically diagnosed on newborn screening, however initial presentation in a newborn would be irritability, poor feeding, vomiting, lethargy, and ketonuria within 48 hours of birth.
Eventually leading to neurologic manifestations of dystonia, seizures, and cerebral edema.
So, I work in the emergency department… why do I care?
Episodes of acute exacerbation can occur in children who are usually controlled by nutritional management
Induced by intercurrent illness, exercise, injury, surgery, or fasting
Clinical manifestations of epigastric pain, vomiting, anorexia, muscle fatigue
Neurologic signs of hyperactivity, sleep disturbance, stupor, decreased cognitive function, dystonia, ataxia (in a child think about loss of previously mastered motor and speech function)
When in doubt, look for the acute onset of sweet smelling urine and send for qualitative urine organic acids to confirm
Aggressive treatment involves lowering concentrations of plasma branched chain amino acids (inhibiting protein catabolism and enhancing protein synthesis)
-IV fluid resuscitation
-treating the inciting cause (for example gastroenteritis, upper respiratory infection, etc.)
-hospital admission for serial neurological exams and monitoring for clearance of amino acids from the urine
Source: Kleopa, K. A., Raizen, D. M., Friedrich, C. A., Brown, M. J. and Bird, S. J. (2001), Acute axonal neuropathy in maple syrup urine disease. Muscle Nerve, 24: 284–287.; picture