ASS deficiency (medical condition)

A very rare urea cycle disorder where a lack of the enzyme argininosuccinate synthetase prevents ammonia being turned into urea which can then be excreted in the urine. The build up of ammonia in the body can cause harmful effects. The neonatal form of citrullinemia type I is generally more serious than the later onset form which may sometimes be mild enough to produce no symptoms. See also Citrullinemia I