Myotonia Congenita - An Overview

Introduction

Myotonia congenita is a rare genetic disease characterized by muscle stiffness, clumsiness, muscle cramps, and weakness. This disease affects the chloride channels on the muscle membrane, thus damaging the electrical process of the muscle. Also known as non-dystrophic myotonia disorder. Unlike other disorders, it does not cause muscle wasting but will cause muscle enlargement and strengthening. In some people, stiffness of muscles is very mild, and in some people, it will lead to severe stiffness, interfering with normal activities like walking and running. Affects one in 1,00,000 births. Mostly affecting men more than females. This condition is more common in northern Scandinavia, occurring in approximately one in 10,000 people.

What Are The Forms Of Myotonia Congenita?

• Thomsen Disease: It is a rare and milder form of myotonia congenita. Symptoms appear from the first few months of life to two to three years old.

• Becker Disease: It is a very common and severe form of myotonia congenita. Becker disease is inherited as an autosomal recessive pattern that means both the genes from both parents are mutated. Symptoms will appear around four to twelve years old. It attacks arms and legs, causing muscle weakness.

Symptoms of Thomsen disease start earlier in life and impact the face and arms formally. Becker disease often starts in later life and firstly will affect the legs.

What Are the Causes of Myotonia Congenita?

Genetic mutation in CLCN1 (skeletal muscle chloride channel gene). The CLCN1 gene shuts the electrical signals from neurons to the skeletal cell, which results in a disrupted flow of chloride ions. For a normally functioning body, skeletal muscles tense in a regular pattern. A defect in the gene keeps the muscles contracted, thus slowing down the relaxation after a voluntary movement.

Myotonia congenita is an inherited disease, either from both parents or any of them. Parents may carry defective genes without realizing they are until children develop the symptoms. If the faulty gene is received from one of the parents, it will result in Thomsen disease, and if received from both parents, it will result in Becker's Disease.

What Are The Signs And Symptoms Of Myotonia Congenita?

• Muscle stiffness and rigidity.

• Frequent muscle cramps.

• Enlarged muscles (hypertrophy of muscles).

• Sudden provoked movements.

• Choking, gagging reflux in young children.

• Children may be clumsy and will fall frequently.

• Chewing, talking, and swallowing is difficult.

• Double vision.

• Abnormal deviation of the eye.

• Stiffness, especially in the eyelid, face, legs, and tongue.

• Generalized weakness or fatigue.

Weakness and larger muscles (athletic appearance) indicate Becker's disease. Men are usually more affected than females and also have more severe symptoms. But women experience the worst symptoms during menstruation and pregnancy.

How To Diagnose Myotonia Congenita?

• Physical Examination and Detailed History: A physical examination is done by the doctor. The doctor will ask about the symptoms and take a detailed family history. The doctor will check for rapid movement of eyes, grip for holding the object and checking for reflexes by tapping on muscles.

• Blood Test: Routine blood test and a special test for enzyme creatinine (any muscle damage will increase the creatinine level).

• Electromyography (EMG): It measures the electrical signals from the muscles. Useful in differentiating between a nerve disorder and muscle disease.

• Gene Testing: It detects genetic mutation that leads to Myotonia congenita.

• Muscle Biopsy: A muscle biopsy takes a small piece of the muscle to study for abnormalities.

Doctors usually rely on signs and symptoms to distinguish between two types of congenital myotonia. However, features of myotonia caused by CLCN1 mutations can coincide with myotonia caused by sodium channel mutation, which results in a similar disease, Para myotonia contents.

What Are The Treatment Options for Myotonia Congenita?

People with myotonia congenita do not require special care, but early intervention can restore muscle strength to its full potential. Basic lifestyle changes can help to reduce the symptoms of myotonia congenita.

• Avoid cold climates or temperature

• Do warm-up exercises regularly, as symptoms reduce once the muscles are warm.

• Avoid stress or stressful environments.

• The diet should consist of soft foods to avoid choking hazards.

• Reduce or avoid any medicines that will worsen the symptoms.

• Take help from a genetic counselor- they will discuss how the disease might be passed to children.

• Medications like Mexiletine (a sodium channel blocker), Carbamazepine (anticonvulsant), Phenytoin (anticonvulsant), Quinine (antimalarial), Dantrolene (muscle relaxant), Acetazolamide (anticonvulsant), and Trimeprazine (antihistamines) help in relaxing the muscles and reducing the stiffness of muscles.

What Care Should Be Taken When a Person Is Suffering From Myotonia Congenital?

• Take steps to improve safety in the house as myotonia congenital can cause frequent falls.

• Make easy and simple adjustments to improve the quality of life

• Pregnant women must see a specialist to manage the condition during and after pregnancy.

• The disorder can be controlled with regular exercise and physical therapy.

• Also, if a family member is diagnosed with myotonia congenital, the entire family and relatives should get tested.

• Care should be taken while undergoing any procedure related to general anesthesia as it has adverse side effects on people suffering from myotonia congenita.

• Take help from the support groups to talk out the problems and boost confidence. Participate in research programs as this can help to search for new medicines.

What Is The Progression Of Myotonia Congenita?

The onset of this disease is in early to late childhood, and someone with this disease can have a long, productive life and even excel in sports where strength is more important than flexibility.

Conclusion

In conclusion, myotonia congenita is a rare genetic disorder characterized by muscle stiffness and delayed muscle relaxation after contraction. This condition can significantly impact an individual's quality of life, affecting their mobility, coordination, and overall muscle function. Throughout this article, we have explored the causes, symptoms, diagnosis, and treatment options for myotonia congenita. Although myotonia congenita is a lifelong condition without a cure, there are various management strategies available to help individuals cope with its symptoms and improve their daily functioning. These may include medication, physical therapy, and lifestyle modifications. Additionally, raising awareness about myotonia congenita is crucial to ensure timely diagnosis, appropriate medical care, and support for affected individuals and their families.