Msud

A. About one in every 200,000 babies in the United States is born with MSUD.

MAPLE syrup urine disease is an inherited disorder of amino-acid metabolism characterized clinically by irritability, rigidity, convulsive seizures and coma commonly manifest in the first weeks of life. Menkes1 found that patients afflicted with this neurological disorder excrete large amounts of branched-chain keto-acids in their urine, and Dancis et al. 2 demonstrated a deficiency in branched-chain keto-acid decarboxylase in leucocytes. This enzyme defect results in the accumulation of branched-chain keto- and amino-acids in the plasma and tissues of these patients

If MSUD is not treated, what problems occur?

There are a number of different forms of MSUD. The most common form, "classic MSUD", can be life-threatening and must be treated promptly to prevent serious health problems. Other forms are less severe. These milder forms are less common. This fact sheet contains information on classic MSUD.

Classic MSUD

Symptoms start as soon as a baby is fed protein, usually shortly after birth. Some of the first symptoms are:

* poor appetite

* weak suck

* weight loss

* high pitched cry

* urine that smells like maple syrup or burnt sugar

Babies with MSUD have episodes of illness called metabolic crises. Some of the first symptoms of a metabolic crisis are:

* extreme sleepiness

* sluggishness

* irritable mood

* vomiting

If not treated, other symptoms can follow:

* episodes where muscles tone alternates between being rigid and floppy

* swelling of the brain

* seizures

* high levels of acidic substances in the blood, called metabolic acidosis

* coma, sometimes leading to death

Symptoms of a metabolic crisis often happen:

* after going too long without food

* during illness or infection

* during stressful events such as surgery

Without treatment, brain damage can occur. This can cause mental retardation or spasticity. Some babies become blind. If not treated, most babies die within a few months.

All infants with classic MSUD present during the neonatal period. For other forms, age of presentation depends on several variables, including dietary protein and calorie intake, growth rate, number and severity of infectious illnesses, and rarely, dietary thiamine intake.

2. In both intermediate and intermittent forms of MSUD, acute biochemical and neurological manifestations can mimic the classic phenotype if physiological stress is sufficient to overwhelm residual BCKAD activity or this activity is reduced by transient changes in the phosphorylation state of the enzyme complex. Even in persons with relatively high baseline residual BCKAD activity, episodes of metabolic intoxication can be fatal.

3. Biochemical