Hyperlysinemia

Hyperlysinemia is an autosomal recessive metabolic disorder marked by an abnormal rise of the amino acid lysine in the blood. It results from mutations in the AASS gene, which encodes alpha-aminoadipic semialdehyde synthase, an enzyme of lysine breakdown. Although the biochemical abnormality is striking, the condition appears to be benign and usually causes no health problems. Some patients have nevertheless been reported with behavioral abnormalities, delayed speech and language development, low muscle tone in infancy, intellectual disability, small head size, seizures, short attention span or short stature, and the disorder has been associated with ectopia lentis, a displaced eye lens. Because inheritance is autosomal recessive, an affected person carries two defective copies of the gene, one from each parent, while the parents usually carry a single copy and show no signs. The related condition saccharopinuria involves the same pathway.