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  • Updated 06.22.2023
  • Released 02.01.1995
  • Expires For CME 06.22.2026




Hereditary galactosemia due to galactose-1-phosphate uridyltransferase (GALT) deficiency is one of the inborn errors of carbohydrate metabolism and can be a life-threatening illness during the newborn period. First described in the United States literature in a variant patient in 1935 by Mason and Turner, galactose-1-phosphate uridyltransferase (GALT) deficiency is the most common enzyme deficiency that causes clinically relevant hypergalactosemia. Removing lactose by stopping breast milk or proprietary formula feedings largely eliminates the toxicity associated with newborn disease, but long-term complications almost always occur in the severe form of GALT deficiency, as reported by Komrower and Lee in 1970, Fishler and colleagues in 1980, and, most convincingly, in the 1990 retrospective survey by Waggoner and colleagues. In this article, the author reviews the clinical, laboratory, and imaging features of this enigmatic disease, including putative biochemical toxicities that center around galactose-1-phosphate and galactitol metabolism.

Key points

• Galactosemia is a medical emergency in the newborn period.

• Dietary lactose restriction usually rescues affected newborn infants, preventing multiorgan toxicity syndrome and eliminating E coli sepsis.

• Prospective dietary therapy does not prevent long-term CNS complications nor does it prevent primary ovarian insufficiency in affected women.

Historical note and terminology

Lactose and galactose. It took several centuries from the first crude isolation of lactose to a fairly complete understanding of its components and their structures.

In 1633, Italian physician Fabrizio Bartoletti (1576–1630) was the first to isolate lactose, although his isolation was somewhat crude (04). In 1700, the Venetian pharmacist Lodovico Testi (1640–1707) advocated milk sugar (saccharum lactis) for the relief of multiple ailments (133). In 1715, Testi's procedure for making milk sugar was published (134). Lactose was identified as a sugar in 1780 by Swedish-German pharmaceutical chemist Carl Wilhelm Scheele (1742–1786) (121).

Swedish-German pharmaceutical chemist Carl Wilhelm Scheele (1742-1786)

Carl Vilhelm Scheele, statue by Johan Börjeson, in Humlegarden in Stockholm, unveiled on December 9, 1892. This picture was found in "Words and Pictures" in 1892. (Courtesy of Wikimedia Commons. Public domain. Image restored an...

In 1812, Heinrich Vogel (1778–1867) recognized that glucose was a product of hydrolyzing lactose (142; 143). Lactose was named by the French chemist Jean-Baptiste André Dumas (1800–1884) in 1843 (37). In 1856, French chemist and microbiologist Louis Pasteur (1812–1895) crystallized the other component of lactose, galactose, but called it “lactose.” In 1860, French chemist Marcellin Berthelot (1827–1907) renamed it "galactose," and transferred the name "lactose" to the disaccharide "milk sugar" (19).

By 1894, German chemist (and later Nobel Laureate) Emil Fischer (1852–1919) had established the configurations of the component sugars, glucose in 1891 and, with Robert Selby Morrell (1867–1946), galactose in 1894 (Fischer 1891a; Fischer 1891b; Fischer and Morrell 1894).

Galactosemia. The first report of galactosemia was by Austrian pediatrician August von Reuss (1879–1954) in 1908; it concerned an infant on breastmilk with failure to thrive, hepatosplenomegaly, and galactosuria (144; 145). The galactosuria resolved after stopping dietary milk products, but the infant ultimately died. Autopsy showed hepatic cirrhosis. In 1917, German pediatrician Friedrich Göppert (1870–1927) reported an infant with poor growth, lactose exposure, and hypergalactosuria (51).

In 1935, American pediatrician Howard Harris Mason MD and Mary E Turner PhD at the College of Physicians and Surgeons, Columbia University, provided the first comprehensive description of the clinical variant form of hereditary galactosemia (95). It was also the first report of a patient with any form of galactosemia due to galactose-1-phosphate uridyltransferase (GALT) deficiency in the American literature. This African-American infant had not been placed on a lactose-restricted diet until 10 months of age. The diet treatment reversed the complications of poor growth, developmental delay, liver disease, and anemia relatively quickly. More infants with classic galactosemia had not been described until 1935 because most untreated babies die of E coli sepsis in the newborn period (10).

This review focuses primarily on hereditary galactosemia due to severe GALT deficiency.

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