Galactosemia

Abstract

Abstract Galactose metabolism involves three enzymes: galactokinase, galactose-1-phosphate uridyl transferase (GALT) and uridine diphosphate-4-epimerase (Fig. 49–1). Inborn errors of metabolism (IEM) have been described for all three enzymes. The most common inborn error in galactose metabolism is deficiency of the GALT enzyme. Its incidence in North America is approximately 1 in 60,000. Galactose levels and/or GALT activity are routinely tested in all infants by newborn screening programs. Infants with elevated galactose and/or decreased enzyme activity should be referred to a biochemical genetics program that specializes in treatment of IEM. This chapter will focus on GALT deficiency since the classical form of the disease requires lifelong dietary treatment. In classical galactosemia, the GALT enzyme is not produced and the affected individual has no enzyme activity. Neonates with untreated classical GALT deficiency present a few days after starting milk-based formula or breast milk feeding. The initial symptoms include poor feeding, vomiting, and jaundice. Failure to thrive, hepatomegaly, edema, splenomegaly, and sepsis can follow. The disease is rapidly fatal if milk feedings continue. For surviving infants, mental retardation and behavioral problems are common.