Aspartylglucosaminuria is a condition that primarily affects mental functioning and movement. This conditions worsens over time. Infants with aspartylglucosaminuria appear healthy at birth, and development is typically normal throughout early childhood. Around the age of 2 or 3, affected children usually begin to have delayed speech, mild intellectual disability, and problems coordinating movements. Other features that develop in childhood include respiratory infections, a protrusion of organs through gaps in muscles (hernia), and a growth spurt resulting in a large head size (macrocephaly).

Intellectual disability and movement problems worsen in adolescence. Most people with this disorder lose much of the speech they have learned, and affected adults usually have only a few words in their vocabulary. Adults with aspartylglucosaminuria often have psychological disorders and may develop seizures.

People with aspartylglucosaminuria may also have bones that become progressively weak and prone to fracture (osteoporosis), an unusually large range of joint movement (hypermobility), and loose skin. Affected individuals tend to have a characteristic facial appearance that includes widely spaced eyes (ocular hypertelorism), small ears, and full lips. The nose is short and broad and the face is usually square-shaped. They often have poor oral health, including infections and gum disease (gingivitis). Children with this condition may be tall for their age, but lack of a growth spurt in puberty typically causes adults to be short with a small head size (microcephaly). Individuals with aspartylglucosaminuria usually survive into mid-adulthood.