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CA12 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

CA12 gene

The CA12 gene provides instructions for making a protein that regulates cellular pH and salt transport in tissues such as the sweat glands, kidneys, and large intestine.

Normal Function

The CA12 gene provides instructions for making a protein called carbonic anhydrase 12 (CA 12), which belongs to a family of proteins known as carbonic anhydrases. These proteins carry out a chemical reaction involving carbon dioxide and water to produce a negatively charged bicarbonate molecule and a positively charged hydrogen atom (a proton). By regulating the levels of these substances, carbonic anhydrases help maintain the correct cellular pH.

CA 12 is found in several tissues, including the sweat glands, kidneys, and large intestine. The protein likely helps regulate the transport of salt (sodium chloride or NaCl) in these tissues. Researchers suggest that channels moving salt in and out of cells are controlled in part by the pH of the cells. By regulating cellular pH, CA 12 may control salt transport; in sweat glands, it is thought to play a role in determining how much salt is released from the body in sweat.

Health Conditions Related to Genetic Changes

Isolated hyperchlorhidrosis

At least one mutation in the CA12 gene causes isolated hyperchlorhidrosis, a condition characterized by abnormally high levels of salt in sweat that can lead to dehydration associated with low levels of sodium in the blood (hyponatremic dehydration). The mutation replaces the amino acid glutamate at position 143 with the amino acid lysine (Glu143Lys or E143K).

The function of the altered protein is reduced to about 70 percent of normal and is more easily inhibited. It is thought that the altered CA 12 is less able to regulate pH and loses its ability to control how much salt is released in sweat. Researchers suggest that other tissues are seemingly unaffected by CA12 gene mutations because these tissues contain other carbonic anhydrases that compensate for the loss of CA 12 function.

Other Names for This Gene

  • CA XII
  • CA-XII
  • carbonate dehydratase XII
  • carbonic anhydrase XII
  • carbonic dehydratase
  • CAXII
  • tumor antigen HOM-RCC-3.1.3

Frequently Asked Questions

Diagnosis involves measuring the sodium and chloride concentration in sweat samples and comparing them to normal ranges. Genetic testing, specifically sequencing of the CA12 gene, confirms the presence of the Glu143Lys mutation. A sweat chloride test alone may not be sufficient, so a combined biochemical and genetic approach is recommended.
Beyond dehydration, chronic salt loss can lead to hyponatremic electrolyte imbalance, which may cause muscle cramps, dizziness, or, in severe cases, seizures. Some studies suggest a possible link between CA12 mutations and mild renal tubular dysfunction, but more research is needed. Regular follow‑up with a nephrologist or metabolic specialist can help detect and manage these potential complications early.
The CA12 mutation (Glu143Lys) reduces the activity of carbonic anhydrase 12, which normally helps regulate pH and salt transport in sweat glands. The impaired enzyme causes the glands to secrete more sodium chloride, resulting in sweat with abnormally high salt content and a higher risk of dehydration.
Patients should maintain adequate fluid intake, especially during hot weather or exercise. Oral rehydration solutions containing sodium and potassium can help replace lost electrolytes. Wearing loose, breathable clothing and avoiding prolonged exposure to high temperatures also reduce excessive sweating. Regular monitoring of blood sodium levels can guide adjustments to fluid and electrolyte replacement.
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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