Hallmark symptoms include abnormal spinal structure, vision problems, coarse facial features, hearing impairment, and intellectual disability.

Because galactosialidosis involves the lysosomes of all cells, it can affect various areas of the body, including the brain, eyes, bones, and muscles.

[citation needed] Individuals who are diagnosed with early infantile galactosialidosis have symptoms that present just before or after birth and tend to be most severe.

[3] Juvenile/adult subtype symptoms include impaired balance or coordination, dark red spots on the skin or angiokeratomas, vision loss, seizures, and muscle jerks or myoclonus.

[4] Cathepsin A is required in this process because within the complex, it prevents neuraminidase-1 and beta-galactosidase from breaking down prematurely, so that they may perform their functions properly.

[citation needed] All individuals diagnosed with galactosialidosis have inherited the condition in an autosomal recessive manner, regardless of age or subtype.

As a result, toxic materials accumulate within the cells of the body due to the lysosomes' inability to perform their functions.

A complete urinalysis can be performed to detect the presence of oligosaccharides,[4] which would pass through the urine as excess amounts accumulate within cells due to lysosomal dysfunction.

[citation needed] A diagnosis can more specifically be confirmed through molecular genetic analysis, which is used to identify a mutation in the CTSA gene.

Once a mutation is detected, the results are combined with a clinical exam and patient symptoms to fully diagnose galactosialidosis.

[9] A prenatal diagnosis was made by Kleijer et al. in 1979 by measuring beta-galactosidase and neuraminidase activities in cultured amniotic fluid cells.

It is also common for patients to establish routine care with a medical geneticist, neurologist, and ophthalmologist[3] depending on the symptoms they are experiencing and the frequency at which they occur.

More recent research has been done to define the demographics and clinical characteristics of the patient population with galactosialidosis, with the ultimate goal of using this information toward a gene transfer treatment study.