Hyperglycerolemia

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Hyperglycerolemia (glycerol kinase deficiency)

Hyperglycerolemia is a rare genetic disorder caused by a deficiency of the enzyme glycerol kinase. When GK isn’t working well, glycerol builds up in the blood and urine. Glycerol is normally used to make fats like triglycerides and glycerophospholipids, so problems with GK can affect fat metabolism.

Genetics and who it affects
- It is usually inherited in an X-linked recessive pattern, so it affects males more often.
- In some cases, a larger deletion that also removes nearby genes can cause additional problems, such as Duchenne muscular dystrophy or adrenal hypoplasia.
- The condition is caused by mutations or deletions in the glycerol kinase gene on the X chromosome (Xp21.3).

Symptoms
- People with hyperglycerolemia can have a wide range of signs: metabolic problems, developmental delays, low muscle tone or muscle weakness, seizures, learning or speech issues, short stature, and skeletal or adrenal problems.
- Infantile forms can be severe with developmental delay and congenital adrenal or muscular issues. Juvenile and adult forms may have milder symptoms or be found by accident.

Diagnosis
- Glycerol levels can be measured in blood and urine.
- The diagnosis is confirmed by genetic testing of the GK gene on the X chromosome.
- GK activity isn’t usually tested in routine labs.

Forms
- Infantile: most severe, often with Xp21 deletions and possible adrenal problems or Duchenne muscular dystrophy.
- Juvenile: uncommon, with variable symptoms.
- Adult: often mild or asymptomatic and found incidentally.

Treatment and management
- There is no cure. Management focuses on symptoms and complications:
- Low-fat diet
- IV glucose during metabolic crises if needed
- Monitoring for insulin resistance or diabetes
- Evaluation for Duchenne muscular dystrophy and adrenal insufficiency
- Developmental support and other supportive care
- Some adults have been treated with fibrates and statins to lower glycerol, but these are not cures.

Prognosis and prevention
- It is genetic, and there is no known way to prevent it.
- The outlook varies; some people have mild symptoms, others face more serious metabolic or developmental challenges.

Additional note
- Sometimes high triglycerides are measured when glycerol is elevated (pseudo-hypertriglyceridemia). Some labs can test glycerol directly or use glycerol-blanked triglyceride methods to avoid confusion.