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Reviewed May 2014
What is isolated hyperchlorhidrosis?
Isolated hyperchlorhidrosis is characterized by the excessive loss of salt (sodium chloride or NaCl) in sweat. In particular, "hyperchlorhidrosis" refers to the high levels of chloride found in sweat, although both sodium and chloride are released. Because the salt is abnormally released from the body in sweat, there are lower than normal levels of sodium in fluids inside the body (hyponatremia). Most infants with isolated hyperchlorhidrosis experience one or more episodes of dehydration with low levels of sodium in the blood (hyponatremic dehydration), which can require hospitalization. These episodes typically follow a mild illness that causes vomiting or diarrhea. Affected infants also have poor feeding and an inability to grow and gain weight at the expected rate (failure to thrive). By early childhood, though, weight and height usually catch up to normal, although the abnormal loss of salt still remains. These individuals may still experience dangerous hyponatremia when they sweat excessively, for example in warm temperatures or when exercising.
While hyperchlorhidrosis can occur as one of several features of other conditions, such as cystic fibrosis, people with isolated hyperchlorhidrosis do not have the additional signs and symptoms of these other conditions.
Read more about cystic fibrosis.
How common is isolated hyperchlorhidrosis?
Isolated hyperchlorhidrosis is a rare condition, although its prevalence is unknown. The condition has been found mostly in the Bedouin population of southern Israel.
What genes are related to isolated hyperchlorhidrosis?
Isolated hyperchlorhidrosis is caused by a mutation in the CA12 gene. This gene provides instructions for making a protein called carbonic anhydrase XII (CA XII), which belongs to a family of related proteins known as carbonic anhydrases. These proteins carry out a chemical reaction that involves the molecules carbon dioxide and water and produces a negatively charged bicarbonate molecule (bicarbonate ion) and a positively charged hydrogen atom (known as a proton). The presence of protons and bicarbonate affect the relative acidity (pH) of cells, which is important for several cellular processes, including the transport of salt into and out of cells. Researchers suggest that by regulating cellular pH in the sweat glands, CA XII is able to control the amount of salt released in sweat.
The CA12 gene mutation involved in isolated hyperchlorhidrosis leads to reduction of CA XII protein function. Researchers speculate that the altered CA XII is less able to regulate pH, and it loses its ability to control how much salt is released in sweat, leading to hyperchlorhidrosis.
Read more about the CA12 gene.
How do people inherit isolated hyperchlorhidrosis?
This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.
Where can I find information about diagnosis or management of isolated hyperchlorhidrosis?
These resources address the diagnosis or management of isolated hyperchlorhidrosis and may include treatment providers.
To locate a healthcare provider, see How can I find a genetics professional in my area? in the Handbook.
Where can I find additional information about isolated hyperchlorhidrosis?
You may find the following resources about isolated hyperchlorhidrosis helpful. These materials are written for the general public.
You may also be interested in these resources, which are designed for healthcare professionals and researchers.
What if I still have specific questions about isolated hyperchlorhidrosis?
Where can I find general information about genetic conditions?
The Handbook provides basic information about genetics in clear language.
These links provide additional genetics resources that may be useful.
What glossary definitions help with understanding isolated hyperchlorhidrosis?
acidity ; atom ; autosomal ; autosomal recessive ; bicarbonate ; Ca ; cell ; chloride ; dehydration ; failure to thrive ; fibrosis ; gene ; hyponatremia ; inherited ; molecule ; mutation ; NaCl ; pH ; population ; prevalence ; protein ; proton ; recessive ; sodium ; sodium chloride
You may find definitions for these and many other terms in the Genetics Home Reference Glossary.
See also Understanding Medical Terminology.
References (4 links)
The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? in the Handbook.