Galactosemia

Etiology

• lack of activity of galactose-1-phosphate uridyl transferase; inability to convert galactose to glucose (note that lactose is converted to galactose, so tx is lactose free diet)
• confirmed by direct measurement of the enzyme in erythrocytes and quantitation of erythrocyte galactose-1-phosphate.
• autosomal recessive; prenatal diagnosis is available.

Presentation

• Affected infants who are fed human milk or cow milk formula usually present within days of birth with vomiting, jaundice, failure to thrive, and hepatomegaly.

• Serum chemistry values are generally normal, although there may be acidosis due to sepsis.

• If lactose-containing feedings continue, the infant may develop cataracts, hepatic cirrhosis, splenomegaly, renal failure, clotting disorders, and edema/ascites.

• Gram-negative sepsis, most commonly with Escherichia coli, may be an early feature.

Management

• lactose-free diet: because lactose is broken down into glucose and galactose.

• In infants, this involves the substitution of casein hydrolysate or soybean formulas for human milk or milk formulas.

• Blood samples should be obtained at intervals to monitor the erythrocyte galactose-1-phosphate (gal-1-P) level, which helps to determine dietary compliance. An acceptable gal-1-P level is at least 4 mg/dL.

• Unless appropriate dietary therapy is initiated, the clinical response to antibiotic therapy in infants who have gram-negative sepsis may be poor.

Prognosis

• If untreated, galactosemia may be fatal.

• Patients who are not diagnosed and treated in the first few months of life often are mentally retarded.

• Children who are diagnosed early and treated successfully generally have an excellent prognosis, both for health and cognitive function.

•  Nonetheless, the majority exhibit language delays/verbal dyspraxia/learning disabilities, and almost all affected girls experience premature ovarian failure. The cause of these complications is not clear.

• Galactosemia is included in the neonatal screening panels of most developed countries.

Differential diagnosis:

• The glycogen storage diseases that are accompanied by hepatomegaly usually present later in infancy and are not associated with gram-negative infections.

• Hyperinsulinemia usually presents with hypoglycemia, which may manifest as a seizure in the neonatal period. Hepatomegaly and sepsis are not associated features.

• Plasma long-chain fatty acids are elevated in the peroxisomal disorders. Among these, Zellweger syndrome can present at birth with profound hypotonia, dysmorphic features, hepatomegaly, and congenital cataracts. Sepsis and presentation after the immediate newborn period are not typical.

• Stool porphyrin measurement is useful in the diagnosis of the porphyrias, which typically present later in childhood and are not characterized by severe illness in infancy.

CHLA Board Review 2005