Definition:
Aspartylglucosaminuria (AGU) is caused by deficiency of the enzyme N-aspartyl-beta-glucosaminidase. This enzyme normally cleaves long sugar chains known as oligosaccharides in the lysosome. When N-aspartyl-beta-glucosaminidase is deficient, as it is in the case of AGU, these long sugar chains build up and eventually lead to the clinical features of AGU. Symptoms may progress in degrees of severity over time.

AGU is prevalent in the Finnish population, where it is estimated to affect 130 individuals of the country's total population of 4.5 million. Incidence worldwide is estimated at one in 2,111,000 births. AGU is one of nine identified Glycoprotein Storage Diseases.

Symptoms:
Symptoms of AGU become present between the two and four years of age. Respiratory infections, clumsiness and/or delay in speech are initial symptoms while normal development occurs in affected children until they enter their teenage years.  At around 13-16 years of age, individuals display mental and motor skill development equal to that of a five or six year old. From puberty through 25-28 years of age, the disorder progresses rapidly, resulting in severe mental retardation.

Coarse facial features, osteoporosis, skeletal abnormalities, connective-tissue impairments and seizures may also occur.

Inheritance Pattern:
AGU is an autosomal recessive disorder.

Testing and Diagnosis
The diagnosis of AGU is made initially by demonstrating increased concentrations of oliogosaccharides, short chains of sugars, that accumulate in the urine.  The diagnosis is then confirmed by measuring the activity of the enzyme aspartylglucosaminidase in the blood or in a skin biopsy.  Mutations can be demonstrated in this gene and used to screen prenatally.

Life Expectancy:
Individuals with AGU develop severe mental retardation in their late 20s. They can expect to live into adulthood.

Treatment:
There is no cure for AGU. Treatment is limited to reducing or controlling symptoms of this disorder.  For example, medication may control seizures.  It is encouraged that individuals with AGU routinely see their genetic counselors, neurological, ophthalmological, and other specialists as symptoms arise, to maintain the control of their effects.

Patient Groups:
International Society for Mannosidosis & Related Diseases
P.O. Box 328
Dexter, MI 48130
www.mannosidosis.org
tel: (734) 449-8222
fax: (734) 449-2282
Terri Klein, Executive Director
info@ismrd.org