Overview
Galactokinase deficiency, also known as galactosemia type 2 or GALK deficiency, is a rare inherited metabolic disorder. It affects the body's ability to break down galactose, a sugar found naturally in milk and dairy products. Normally, an enzyme called galactokinase helps convert galactose into a form the body can use. When this enzyme is missing or not working properly, galactose builds up in the blood and tissues — especially in the lenses of the eyes. The most common and often the only major symptom of galactokinase deficiency is the development of cataracts, which are cloudy areas in the lens of the eye. These cataracts can appear very early in life, sometimes within the first few weeks after birth. If not caught and treated quickly, they can lead to permanent vision problems or even blindness. Unlike the more severe classic galactosemia (type 1), galactokinase deficiency does not typically cause liver damage, intellectual disability, or life-threatening illness. The good news is that treatment is straightforward and very effective: removing galactose from the diet — mainly by switching to a lactose-free or galactose-free formula in infants — can stop cataracts from getting worse and may even allow early cataracts to clear up. With early diagnosis through newborn screening and prompt dietary changes, most children with galactokinase deficiency can live healthy, normal lives. Cataract surgery may be needed if vision is already affected.
Key symptoms:
Cataracts (cloudy lens in one or both eyes) appearing in infancy or early childhoodBlurry or reduced visionSensitivity to bright lightDifficulty focusing, especially in infants (may appear as poor eye contact or not following objects)Elevated galactose levels in the bloodGalactose or galactitol detected in the urinePseudotumor cerebri (increased pressure in the skull) — rare
Clinical phenotype terms (26)— hover any for plain English
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Neonatal
Begins at or shortly after birth (first 4 weeks)
Treatments
No FDA-approved treatments are currently listed for Galactokinase deficiency.
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Specialists
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Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
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Questions for your doctor
Bring these to your next appointment
- Q1.Does my child need to avoid all dairy products, or are there some that are safe in small amounts?,How often should my child have eye exams to check for cataracts?,Will my child need cataract surgery, and if so, when is the right time?,Are there any other health problems I should watch for as my child grows older?,Should other family members be tested for this condition?,How do I make sure my child gets enough calcium and other nutrients without dairy?,Is this condition included in our country's newborn screening program, and what does a positive screen mean for our family?
Common questions about Galactokinase deficiency
What is Galactokinase deficiency?
Galactokinase deficiency, also known as galactosemia type 2 or GALK deficiency, is a rare inherited metabolic disorder. It affects the body's ability to break down galactose, a sugar found naturally in milk and dairy products. Normally, an enzyme called galactokinase helps convert galactose into a form the body can use. When this enzyme is missing or not working properly, galactose builds up in the blood and tissues — especially in the lenses of the eyes. The most common and often the only major symptom of galactokinase deficiency is the development of cataracts, which are cloudy areas in the
How is Galactokinase deficiency inherited?
Galactokinase deficiency follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Galactokinase deficiency typically begin?
Typical onset of Galactokinase deficiency is neonatal. Age of onset can vary across affected individuals.