Congenital Myopathies

Treatment

There is no cure for these diseases. Treatment is aimed at relieving symptoms and trying to give the patient the best quality of life possible. Treatment depends on the type of congenital myopathy (see information on some common types below). Some patients will require intensive hospital care, including respiratory support, at least for a time. Other patients may only need to make lifestyle modifications or work with a physical therapist. Yet others may need orthopedic surgery or bracing.

Medications may be available to alleviate symptoms for some patients, although they won't affect the underlying disease.

Advances in gene therapy hold promise for eventually treating congenital myopathies at their source by repairing or replacing defective genes. Likewise, stem cell therapy opens the possibility of replacing diseased muscle cells with healthy ones.

Types of Myopathy

Myotonia Congenita (Becker-type Myotonia or Thomsen's Disease)

Symptoms usually appear in early to late childhood and can include:

• Delayed muscle relaxation
• Muscle stiffness, usually worse with sudden movements after rest
• Difficulties with walking, grasping or chewing
• Muscle enlargement

Treatment will depend on the severity of the patient's muscle stiffness and may include exercises to relax the muscles, or possibly medication.

Paramyotonia Congenita (Eulenberg's disease)

Symptoms usually appear at birth and can include:

• Episodes of muscle stiffness and weakness, usually in the face, neck and upper extremities, lasting from minutes to hours
• Stiffness brought on by exercise or by cold
• Weakness or paralysis brought on by extended exercise or by cold

Episodes of muscle stiffness or weakness triggered by exercise or cold can largely be avoided by behavior modification. For patients whose episodes don't appear to have triggers, medication may be an option.

Hyperkalemic Periodic Paralysis (high blood potassium levels)

Symptoms usually begin to appear in childhood and can include:

• Episodes of general weakness, lasting from 15 minutes to a day or more, possibly recurring daily
• Episodes after rest preceded by vigorous exercise
• Episodes that are aggravated by stress, pregnancy, or foods high in potassium
• Episodes decline in frequency with age

Hypokalemic Periodic Paralysis (low blood potassium levels)

Symptoms usually begin to appear in childhood or adulthood:

• Episodes of severe general weakness, in some cases nearly complete paralysis
• Episodes that usually occur in the morning — during waking — or at night
• Episodes ranging in frequency from daily to only a few in a patient's lifetime

Patients with hyperkalemic or hypokalemic periodic paralysis can reduce episodes with appropriate dietary modifications, avoiding especially strenuous exercise and cooling down slowly after moderate exertion. Medication may also be helpful.

Central Core Disease

Symptoms usually appear at birth and can include:

• Poor muscle tone
• Persistent muscle weakness
• Delayed ability or inability to walk
• Skeletal deformities due to chronic muscle weakness, such as joint dislocations or curvature of the spine (scoliosis)

Patients with central core disease also are at risk for malignant hyperthermia, a potentially fatal reaction to certain anesthetic drugs.

Treatment for central core disease will depend on the severity of the patient's symptoms. Some patients may only need physical therapy; others may need orthopedic surgery or require a walker or other support device. Exercise is usually helpful. If surgery is required, patients with central core disease may need alternative anesthetic drugs to avoid the risk of malignant hyperthermia.

Nemaline Myopathy (Rod Body Disease)

Symptoms can appear at birth, in childhood, or even adulthood and may include:

• Poor tone and weakness in the muscles of the face, neck and upper limbs
• Delayed ability or inability to walk
• Increased weakening at puberty, possibly necessitating use of a wheelchair
• Respiratory problems
• Heart problems
• Swallowing and speech problems
• Skeletal deformities due to chronic muscle weakness, such as joint dislocations or curvature of the spine (scoliosis)

Infants with nemaline myopathy usually require a feeding tube and respiratory support. Respiratory support may also be prescribed for children and adults to avoid respiratory failure during sleep. Physical and orthopedic therapies can help improve strength and mobility.

Myotubular Myopathy (Centronuclear Myopathy)

Symptoms can appear at birth, in childhood or in adulthood depending on the inheritance pattern. X-linked myotubular myopathy affects only boys and can cause:

• Severe muscle weakness (though as they age, boys may gain muscle strength)
• Delayed or inability to walk
• Feeding and respiratory difficulties
• Lung infections
• Problems with other organ systems, causing anemia, gallstones, liver abnormalities

Patients with autosomal forms usually have milder muscle problems, but problems can worsen with age. Other organ systems, however, usually aren't affected.

Until recently, infants with X-linked myotubular myopathy were not expected to live beyond their first few months. Now, however, with intensive, continuous feeding and ventilation support, more infants survive and may even enjoy a high quality of life. Patients with autosomal forms of myotubular myopathy may also require monitoring and respiratory support and usually benefit from physical and orthopedic therapies.