Galactosemia – Source, Symptoms, Detection, Therapy, Diet

Galactosemia represents a cluster of uncommon, genetically determined carbohydrate metabolism disorders transmitted through an autosomal recessive inheritance pattern. The pathophysiological basis of this condition lies in the congenital impairment or complete absence of functional activity in one of three critical enzymes responsible for catalyzing the conversion of galactose into glucose—an enzymatic deficiency that culminates in the clinical presentation recognized as classical galactosemia, as substantiated by medical literature references (sources: publication 1 and 3).

The primary pathogenic factor underlying classical galactosemia is an **inherited deficiency in the enzymatic activity of galactose-1-phosphate uridylyltransferase (GALT)**, a critical catalyst within the **Leloir pathway** responsible for converting galactose into glucose. As a direct consequence of this enzymatic insufficiency, there occurs a **progressive systemic accumulation of unmetabolized galactose** alongside its deleterious metabolic byproducts, including **galactose-1-phosphate** (the substrate of the GALT-catalyzed reaction), **galactitol** (a sugar alcohol formed via aldose reduction), and **galactonic acid** (an oxidation product of galactose). The buildup of these compounds triggers **multiorgan damage**, particularly affecting the liver, kidneys, brain, and ocular lens, due to their direct cytotoxic effects and disruption of cellular osmotic equilibrium.

The initial clinical presentations of galactosemia, triggered by the ingestion of breast milk or lactose-containing infant formulas, typically emerge between the second and fourth day of a newborn’s life. This metabolic disorder arises from an enzymatic deficiency that impairs the proper breakdown of galactose, resulting in the accumulation of harmful metabolic byproducts. The consequence is progressive damage to internal organs, including the liver (with compromised detoxification capacity), kidneys (with potential risk of failure), eye lenses (which may lead to early-onset cataracts), and the central nervous system [3]. In infants, the condition manifests as a marked reduction in feeding tolerance, recurrent episodes of vomiting, and failure to thrive despite consistent feeding efforts. Additionally, the toxic effects of metabolites on hepatocytes induce cholestatic jaundice, characterized by yellowing of the skin and sclera. Physical examination often reveals abdominal distension due to hepatosplenomegaly. Over time, without appropriate intervention, the disorder may progress to psychomotor developmental delays, irreversible neurodegenerative alterations in the brain, skeletal mineralization defects (such as osteoporosis or osteopenia), and premature ovarian insufficiency in females, potentially resulting in infertility during later life stages [1, 3, 4].

Comprehensive neonatal screening procedures performed during the initial days following birth facilitate the prompt identification of the condition and the immediate implementation of appropriate therapeutic measures. The cornerstone of diagnosing the classical variant of galactosemia lies in demonstrating either the complete absence or a markedly diminished enzymatic activity of GALT (galactose-1-phosphate uridylyltransferase) within dried blood spot samples, achieved through the application of a specialized diagnostic assay developed by Beutler and Baluda, as referenced in scientific publications numbered [2] and [4].

The cornerstone of galactosemia treatment lies in the complete exclusion of galactose—a monosaccharide constituent of lactose—from the patient’s dietary regimen. Implementation of a stringent lactose-free diet, devoid of all dairy products and their derivatives, during the earliest phases of the disorder facilitates the resolution of most clinical manifestations, with the exception of permanent neurocognitive impairments, which remain irreversible [1]. Consistent adherence to a lactose-free nutritional protocol substantially diminishes mortality rates associated with *Escherichia coli*-induced sepsis, as the bacterial proliferation is exacerbated by the accumulation of galactose-1-phosphate. Given the elevated lactose content in human breast milk, galactosemia constitutes an absolute contraindication to breastfeeding—even minimal exposure may precipitate acute metabolic crises. Upon suspicion of the condition, immediate cessation of natural feeding is mandatory, followed by the introduction of specialized lactose-free infant formulas tailored to the metabolic requirements of enzyme-deficient infants.

The dietary management of patients diagnosed with galactosemia necessitates the complete exclusion of galactose- and lactose-containing products, which are inherently present in mammalian milk. During the neonatal period and early childhood, the cornerstone of therapeutic intervention involves replacing breast milk with specialized lactose-free formulations, such as protein hydrolysates or soy-based infant formulas. Lactose, commonly referred to as milk sugar, constitutes a fundamental component of all mammalian milk, thereby necessitating meticulous dietary adjustments. As the child’s diet is gradually expanded, it is imperative to eliminate all sources of galactose, including dairy products (e.g., yogurt, kefir, cream, cheese, and butter). It should be noted that galactose is also prevalent in numerous plant-based foods, rendering its complete eradication from the diet virtually unfeasible. According to expert guidelines, a strictly galactose-free diet permits a daily intake of up to 125 mg of free galactose, primarily derived from fruits and vegetables. This article additionally outlines a comprehensive list of permitted and prohibited food items and underscores the necessity of calcium and vitamin D supplementation for patients adhering to an elimination diet.