Aspartylglucosaminuria (AGU) is an inherited lysosomal storage disorder that affects the brain, bones, and connective tissue. This is due to a deficiency of the enzyme aspartylglucosaminidase. Children with AGU are normal for the first few years of life. They develop progressive intellectual disability that greatly affects speech. Other symptoms include weak bones that break easily, loose joints and skin, and frequent infections. Adults with AGU may have seizures and movement problems. Individuals with AGU usually survive into mid-adulthood. There is no cure for AGU; however medical surveillance and care may help to improve some symptoms and overall condition of life. AGU is caused by pathogenic variants in the AGA gene.