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CLCN1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

CLCN1 gene

The CLCN1 gene provides instructions for a chloride channel essential for skeletal muscle function, with mutations causing myotonia congenita.

Normal Function

The CLCN1 gene provides instructions for making a type of protein called a chloride channel. These channels, which transport negatively charged chlorine atoms (chloride ions), play a key role in a cell's ability to generate and transmit electrical signals.

The CLCN1 gene provides instructions for making a chloride channel called ClC-1. These channels are found only in muscles used for movement (skeletal muscles). For the body to move normally, skeletal muscles must tense (contract) and relax in a coordinated way. Muscle contraction and relaxation are controlled by the flow of certain ions into and out of muscle cells. ClC-1 channels, which span the cell membrane, control the flow of chloride ions into these cells. This influx stabilizes the cells' electrical charge, which prevents muscles from contracting abnormally.

Health Conditions Related to Genetic Changes

Myotonia congenita

More than 150 mutations in the CLCN1 gene have been identified in people with myotonia congenita. This condition is characterized by abnormally sustained muscle contractions, known as myotonia.

  • Becker disease: Most CLCN1 mutations cause the autosomal recessive form of the disorder. These mutations change the structure or function of both protein subunits that make up the ClC-1 channel, greatly reducing the flow of chloride ions into skeletal muscle cells and triggering prolonged muscle contractions.
  • Thomsen disease: This is the autosomal dominant form of the disorder. Mutations change one of the two protein subunits that make up the ClC-1 channel. The altered protein takes on new, harmful properties that disrupt the ability of both subunits to regulate chloride ion flow.

Other Names for This Gene

  • chloride channel 1, skeletal muscle
  • Chloride channel protein 1
  • Chloride channel protein, skeletal muscle
  • chloride channel, voltage-sensitive 1
  • ClC-1
  • CLC1
  • CLCN1_HUMAN
  • MGC138361
  • MGC142055
  • skeletal muscle chloride channel 1

Frequently Asked Questions

Myotonia congenita typically causes delayed muscle relaxation that is noticeable right after a sudden movement (e.g., gripping a door handle, rising from a chair) and improves with repeated activity (“warm‑up” phenomenon). Unlike fatigue, the stiffness is present at rest and may be triggered by cold, stress, or certain medications. A neurologist can confirm the diagnosis with electromyography (EMG) showing characteristic myotonic discharges and, if needed, genetic testing for CLCN1 mutations.
Common triggers include cold temperatures, high‑carb meals, stress, fatigue, and certain drugs (e.g., anesthetics, some antiarrhythmics). To reduce episodes, keep your environment warm, avoid rapid temperature changes, eat balanced meals with moderate carbs, manage stress with relaxation techniques, and discuss any new medications with your doctor. Regular low‑impact exercise can also improve muscle conditioning and lessen stiffness over time.
Testing usually involves a blood sample sent for targeted sequencing of the CLCN1 gene. A pathogenic mutation confirms the diagnosis and clarifies whether the inheritance pattern is autosomal dominant (Thomsen) or recessive (Becker). If you have a dominant mutation, each child has a 50 % chance of inheriting it; with a recessive mutation, both parents must be carriers, giving each child a 25 % risk. Genetic counseling can help you understand reproductive options, including prenatal testing or pre‑implantation genetic diagnosis.
First‑line drug therapy often includes mexiletine (a sodium‑channel blocker) or, in some cases, carbamazepine or phenytoin. Physical therapy focused on stretching and gradual strengthening can improve functional mobility. Some patients benefit from avoiding caffeine and alcohol, which may exacerbate stiffness. Always discuss medication choices and dosing with a neurologist experienced in channelopathies.
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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