Hyperlysinuria With Hyperammonemia

Abstract

Dibasicaminoaciduria with hyperammonemia was observed in a mentally and physically retarded patient. Oral loading test results revealed diminished capacity to absorb lysine compared to five normal controls and served to distinguish this patient from those with familial protein intolerance. Fasting plasma arginine and lysine concentrations were decreased to 10% to 50% of normal values, presumably because of decreased intestinal absorption and increased renal excretion. The severe postprandial hyperammonemia may be due to a lack of substrate (arginine) for urea cycle activity. Arginine and lysine deficiency may impair protein synthesis and this factor may be involved in the observed physical and mental retardation. The patient is an example of a previously unrecognized syndrome characterized by dibasicaminoaciduria with defective intestinal absorption of lysine, severe postprandial hyperammonemia with seizures, mental retardation, and subnormal growth and physical development.