Aspartylglycosaminuria

Aspartylglycosaminuria (AGU) is an inborn error of metabolism caused by deficient activity of the enzyme aspartylglucosaminidase. Clinical manifestations consist of psychomotor retardation, coarse facies, hepatosplenomegaly, ventral hernia and skeletal abnormalities. It is a member of Finnish disease heritage, a group of diseases or syndromes caused by mutation in a single gene characterized by higher frequency in Finland than the rest of the world.

Pathophysiology
Deficiency of the aspartylglucosaminidase (1-aspart-amido-beta-N-acetylglucosamine aminohydrase (E.C.3.5.1.26), an enzyme which cleaves the N-acetyl-glucosamine-asparagine linkage of oligosaccharide chains in glycoprotein and glycopeptide metabolism. Biochemical tests show high urinary levels of aspartylglucosamine and low activity of aspartylglucosaminidase.

Epidemiology
Originally, most early patients were of Finnish ancestry but later cases were reported in other groups. After trisomy 21 and fragile X syndrome, this is the most frequent multiple congenital anomaly/mental retardation syndrome.

AGU