Complications

For reasons unknown, children may still develop intellectual disabilities even on a restricted diet. A learning disability is a significant gap between a person's intelligence and the skills achieved at that age. Such life-long conditions can affect school or work, social life, and daily routines. Symptoms may include delay in language acquisition, difficulty with fine and gross motor skills, attention, and difficulty with reading and arithmetic. Around 60% of children with classic galactosemia develop some form of speech disorder as well. However, it is important to keep in mind that development occurs at different rates—a neurological impairment (e.g., fine motor issues) may "disguise" what seems to be a learning disability (e.g., trouble writing numerals but understanding math). Children may have single learning problems or many overlapping issues.

Alongside speech and language disabilities, neurodevelopmental delays have been observed in galactosemia patients, including problems with gait, balance, and fine motor tremors. Such involuntary muscle contractions can affect the hands, head, face, trunk, vocal cords, and legs, leading to functional disabilities. Additional impairments concerning the musculoskeletal system include inaccurate estimation of physical distance during muscular activity (dysmetria) and the inability to coordinate voluntary movements (ataxia). This cascade of effects can impair simple acts in daily life, such as walking, balancing, verbal articulation, etc.

A cataract is a cloudy area in the lens of the eye, which helps focus vision and refract light rays. Clouded vision caused by cataracts can make it more difficult to read, drive at night, and discern the face of someone next to the patient. Cataracts may form in one or both eyes and develop at varying rates. Though cataracts usually do not disturb vision early on, failure to restrict galactose in the diet may cause newborns with classic galactosemia to have eyesight issues. Cataracts usually do not develop in children with galactosemia who are on a restricted diet, but surgery to remove the lens is sometimes necessary in rare cases.

Almost all females with classic galactosemia develop premature ovarian insufficiency, a condition where the ovaries stop releasing eggs earlier in life (early menopause). Though the cause of the high rate of ovarian failure is unknown, it is believed that a byproduct of galactose in the blood may be toxic to the ovaries. As a result, most female patients are unable to have children.