Galactosemia is an inherited autosomal recessive inability to convert galactose to glucose. As a consequence of this inability, excessive galactose accumulates in body tissues, with further metabolic conversion of galactose to galactitol (dulcitol), the sugar alcohol product of galactose. Galactosemia can result from defects in 1 of the 3 enzymes involved in the metabolism of galactose. The most common and the most severe form, known as classic galactosemia, is caused by a defect in galactose-1-phosphate uridyltransferase.
Figure 5-20 “Oil droplet” bilateral cataracts in a patient with galactosemia.
In cases of classic galactosemia, symptoms of malnutrition, hepatomegaly, jaundice, and intellectual deficiency present within the first few weeks of life. The disease is fatal if undiagnosed and untreated. The diagnosis of classic galactosemia can be confirmed by demonstration of galactose in the urine.
Typically, the nucleus and deep cortex become increasingly opacified in individuals with this condition, causing an “oil droplet” appearance on retroillumination (Fig 5-20). The cataracts can progress to total opacification.
Treatment of galactosemia includes elimination of milk and milk products from the diet. In the majority of cases, early cataract formation can be reversed by timely diagnosis and dietary intervention; other cases may require cataract surgery. The oil droplet appearance in classic galactosemia differs markedly from the similarly named oil droplet cataract of posterior lenticonus. In posterior lenticonus, it is a bulge in the posterior capsule that causes the oil droplet appearance on red reflex examination.
Karadag N, Zenciroglu A, Eminoglu FT, et al. Literature review and outcome of classic galactosemia diagnosed in the neonatal period. Clin Lab. 2013;59(9–10):1139–1146.
Excerpted from BCSC 2020-2021 series: Section 11 - Lens and Cataract. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.