Galactokinase Deficiency

What else is it called?

  • GALK deficiency  
  • Galactosemia 2 
  • Hereditary galactokinase deficiency  
  • Galactokinase deficiency galactosemia  
  • GALK-D 
  • GALK 
  • Galactosemia II 
  • Galactosemia type 2  

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What causes it?

Food such as milk products and some fruits and vegetables contain the sugar galactose. The sugar is broken down in the body by enzymes including galactokinase 1. Galactokinase deficiency is caused by a mutation (change) in the GALK1(17q24) gene which is responsible for coding of the galactokinase 1 enzyme. This leads to galactokinase 1 not working properly or missing completely. 

 When the enzyme does not properly, galactose cannot be broken down. This will lead to large amounts of undigested sugars being built up, mainly in the lens of the eye. This can result in damage to the eyes and lead to blurred vision.  

How common is it?

GALK-D is a very rare metabolic disorder. The exact prevalence of the disorder is unknown however the disorder is estimated to occurs in less than 1 out of every 100,000 births.  

What are the signs and symptoms?

  • Delayed growth  
  • Raised levels of plasma galactose 
  • Raised levels of excretion of galactitol through urination  
  • Cataracts (clouding of the eye) 
  • Intracranial pressure (rise in pressure inside the skull) 
  • Prolonged neonatal (newborn) jaundice (yellowish tinge to the skin and whites of eyes)  

The first thing that is usually noticed in babies with GALK is delayed growth. Patients with the disorder have raised levels of plasma galactose and an increased excretion of galactitol through urination. The patients will develop cataracts (clouding of the lens of the eye) in the first weeks or months of their life. This is due to a build up of galactitol in the lens.  

Patients are usually otherwise healthy. However, 5-29% of patients have been reported to have increased intracranial pressure (rise in pressure inside the skull) and some patients experience prolonged neonatal (newborn) jaundice (yellowish tinge to the skin and whites of the eyes). 


How is it diagnosed?

The disorder is usually detected through newborn screening or suspected in babies with cataracts. The diagnosis can be confirmed with biochemical and molecular genetic testing. The disorder can also be diagnosed through specialised blood testing. Blood tests will show high levels of galactose and low levels of enzyme activity.  

Although GALK is included in the newborn screening in the US, it is currently not part of the newborn screening in the UK. 

Can it be treated?

GALK is treated through a restriction of diet. Any dietary changes require a specialist dieticians’ advice and monitoring. All food containing galactose (a sugar found in milk and some fruits and vegetables) need to be avoided in order to prevent a toxic build up of undigested sugars in the blood.  

Your baby’s doctor can suggest foods and formulas that do not contain galactose. This dietary treatment will usually have to be continued through adulthood.  

Your doctor may prescribe calcium, Vitamin C and Vitamin K supplements as the patient must avoid milk-containing products.  

The development of cataracts can be prevented if a diagnosis is made early and a galactose-restricted diet is strictly followed. Children with an early and ongoing treatment can decease the complications of vision trouble.  

Without any treatment, individuals with GALK risk developing cataracts which can lead to reduced vision.

Do my family need to be tested?

Beta-Enolase deficiency is an inherited condition. Humans have chromosomes made up of DNA. Genes are pieces of DNA that carry the genetic information. Each chromosome may have several thousand genes. We inherit chromosomes from the egg of the mother and sperm of the father. The genes on those chromosomes carry the instructions that determine a person’s characteristics, which are a combination of the parents. 

Carriers of the condition do not have the disorder because the other gene of this pair is working normally. Parents of children with Beta-Enolase deficiency are carriers.  

The pattern of inheritance in this condition is autosomal recessive. This means:  

When both parents are carriers, the risk to the baby in each pregnancy is 

  • 25% chance (1 in 4) of developing the condition 
  •  50% chance (1 in 2) for the baby to be a carrier of the condition 
  •  25% chance (1 in 4) for the baby to have two working genes and neither have the condition nor be a carrier 

Relevant Organisations


References are available on request. Please contact us by phoning 0845 241 2173 or emailing [Resource Library No: GCM007].

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