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XK gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

XK gene

The XK gene produces a protein found in various tissues and on red blood cells, and mutations in this gene are linked to McLeod neuroacanthocytosis syndrome.

Normal Function

The XK gene provides instructions for producing a protein that is found in various tissues of the body, particularly the brain, muscle, and heart. This protein is also present on the surface of red blood cells and carries a molecule known as the Kx blood group antigen. Blood group antigens are found on the surface of red blood cells and determine a number of blood types. When blood cells with unfamiliar antigens enter the bloodstream, the body's immune system recognizes the cells as foreign and may trigger an immune reaction that destroys the foreign blood cells.

The function of the XK protein is unclear; researchers believe that it might play a role in transporting substances into and out of cells. On red blood cells, the XK protein attaches to another blood group protein, the Kell protein. The function of this blood group complex is unknown.

Health Conditions Related to Genetic Changes

McLeod neuroacanthocytosis syndrome

Approximately 30 mutations in the XK gene have been found to cause McLeod neuroacanthocytosis syndrome. Most of these mutations lead to the production of an abnormally short, nonfunctional XK protein or cause no XK protein to be produced at all. Missing or abnormal XK protein also affects another blood group antigen, the Kell protein, causing it to be less prevalent on the surface of red blood cells. How mutations in the XK gene cause the misshapen red blood cells and movement problems characteristic of McLeod neuroacanthocytosis syndrome is unknown.

Other Names for This Gene

  • Kell blood group precursor (McLeod phenotype)
  • KX
  • Kx antigen
  • membrane transport protein XK
  • X-linked Kx blood group (McLeod syndrome)
  • X1k
  • XK, Kell blood group complex subunit (McLeod syndrome)
  • XK-related protein 1
  • XK_HUMAN
  • XKR1

Frequently Asked Questions

McLeod neuroacanthocytosis syndrome typically presents with a combination of neurological, psychiatric, and hematological symptoms. Neurological symptoms often include involuntary movements (chorea), muscle weakness, seizures, and difficulty with coordination, usually appearing in adulthood (30s-50s). Psychiatric symptoms like depression, anxiety, and behavioral changes can also occur. Hematologically, individuals may have acanthocytosis (spiky red blood cells) and a specific blood group phenotype.
Currently, there is no cure for McLeod neuroacanthocytosis syndrome, and treatments focus on managing symptoms. Neurological symptoms like involuntary movements (chorea) can sometimes be managed with medications such as tetrabenazine or antipsychotics. Seizures are treated with anti-epileptic drugs. Physical therapy, occupational therapy, and speech therapy can help maintain function and improve quality of life. Regular monitoring by a neurologist is essential to adjust treatment as the condition progresses.
In McLeod syndrome, mutations in the XK gene lead to the absence of the Kx blood group antigen and reduced expression of the Kell protein on red blood cells. This is crucial for blood transfusions because individuals with McLeod syndrome may develop antibodies against normal Kell antigens if they receive standard blood transfusions. Therefore, they require Kx-negative and Kell-negative blood for transfusions to prevent severe transfusion reactions. It's vital to inform healthcare providers about this specific blood type.
Diagnosis of McLeod neuroacanthocytosis syndrome often involves a combination of clinical evaluation, blood tests, and genetic testing. Blood tests may show elevated creatine kinase levels and the characteristic acanthocytes (spiky red blood cells). The absence of the Kx antigen and reduced Kell protein on red blood cells is a key indicator. Definitive diagnosis is confirmed by genetic testing to identify mutations in the XK gene. Neurological imaging (MRI) and nerve conduction studies may also be used to assess brain and nerve involvement.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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