What is galactosemia, and how does it affect humans?

Galactose is a simple sugar that forms half of the disaccharide lactose, the sugar commonly found in milk. When we consume dairy products, lactose is broken down into glucose and galactose by the enzyme lactase during digestion. The metabolism of galactose in the human body is a critical process, involving several steps catalyzed by different enzymes. One of these enzymes is galactose-1-phosphate uridyltransferase (GALT), which facilitates the conversion of galactose to glucose-1-phosphate. This conversion is a part of the Leloir pathway, a metabolic pathway that is responsible for the proper utilization and detoxification of galactose.

Failure in this pathway, such as a deficiency in GALT, leads to galactosemia. The disruption causes inefficient conversion of galactose, leading to a dangerous build-up. Normal metabolism of galactose is vital because it ensures that the body can use sugar efficiently to generate energy, and prevents toxic levels of unmetabolized sugars from accumulating in the blood.

Galactosemia is classified as an inherited metabolic disorder. This means the condition is passed down through families and is caused by mutations in genes that encode for enzymes necessary for metabolizing certain substances—in this case, galactose. The disorder is most commonly inherited in an autosomal recessive pattern. This implies that a child must inherit two copies of the mutated gene, one from each parent, in order to have the condition.

Genetic Screening and Diagnosis

Early detection is vital. Newborns are typically screened for galactosemia shortly after birth, allowing for early intervention. Diagnosis often involves looking for enzyme activity in red blood cells or mutation testing of the GALT gene. Understanding the genetic basis helps to manage the disorder and provides information for family planning, as siblings and offspring of affected individuals have higher risks of carrying or inheriting the disease.

The primary treatment for managing galactosemia is adhering to a galactose-free diet. Given the inability to metabolize galactose, eliminating this sugar from the diet helps prevent the symptoms and complications associated with the condition.

Patients with galactosemia must avoid all forms of dairy, as well as other foods that contain lactose. Moreover, some fruits and vegetables also contain galactose and must be restricted. Special lactose-free formulas are available for infants, which are crucial for their growth and development without the risk of galactose accumulation.

Importance of Diet Adherence

Maintaining this diet strictly is essential for preventing long-term complications such as intellectual disability, liver disease, and ovarian failure. Regular follow-ups with healthcare providers, including dietitians, can ensure that the nutritional needs are met while avoiding galactose. Label-reading and education on hidden sources of galactose in foods can help individuals with galactosemia manage their diet effectively.