Pseudohypertrophic Myopathy - Causes, Symptoms, and Mangement

Introduction:

Pseudohypertrophy is a condition in which muscles enlarge due to the deposition of fat instead of muscle fibers. This condition is also known as Duchenne muscular dystrophy. This condition occurs due to genetic mutations that affect protein metabolism. This error in protein production leads to abnormal muscle development. The symptoms begin to surface in early childhood, and males are more likely to be affected by this disorder. The disease can progress considerably through teenage and cause muscle loss, affecting motor function. The affected individual may require the help of a wheelchair in the later stages of this disease.

What Causes Pseudohypertrophic Myopathy?

Mutations (changes in the structure of genes) are responsible for protein production cause dysfunction of the muscle fibers. Proteins are necessary to form healthy muscles. In this disorder, the gene responsible for protein production becomes faulty. Pseudohypertrophic myopathy is an X-linked disease. Each cell consists of two sex chromosomes, X and Y chromosomes. X- linked disorders are caused due to variations in the genes present on the X chromosome. In females, there are two X chromosomes (XX); in males, there are X and Y chromosomes (XY). Variations in at least one X chromosome are required to develop this disorder.

What Are the Symptoms of Pseudohypertrophic Myopathy?

The symptoms start appearing in early childhood. Impairment in muscle function is commonly seen in the leg muscles, feet, pelvic girdle, lower back, and lower abdominal regions. Muscular atrophy (decrease in the size of the muscles or muscle wasting) is also very common in these patients. Symptoms may occur in the shoulders as the disease progresses. The following are the symptoms of pseudohypertrophic muscular dysfunction -

• Muscle weakness.

• Loss of muscle tone leads to frequent falls.

• Difficulty getting up from a sitting position or climbing stairs (Gower's sign).

• Problems with balance and coordination.

• Uneven gait (walk).

• Muscle pain and stiffness.

• Difficulty in running and jumping.

• Abnormal enlargement of the calf muscles is seen in toddlers due to scarring of muscles. Other muscles may also appear bulky.

Duchenne Muscular Dystrophy in Children -

Children may delay reaching developmental milestones, such as sitting unsupported. They may start walking on their toes and have a waddling gait. As the disease progresses, curving of the spine (scoliosis or lordosis) is observed with subsequent wasting of the thigh and pectoral (chest) muscles. Deformity of the muscle fibers leads to restricted movements of the limbs. By the age of 10 or 12 years, the individual may require assistance walking or a wheelchair. The affected children have reduced bone density and are more prone to developing fractures.

Chronic complications such as respiratory (breathing) and cardiac (heart) problems may also occur. Cardiomyopathy is the deterioration of the heart muscles that leads to irregular heartbeats and affects the ability of the heart to pump blood efficiently, leading to heart failure. The patients are more prone to respiratory infections such as pneumonia, which cause respiratory failure. In severe cases, the muscles of the intestines may also get affected by this disorder and cause dysmotility (slow passage of food through the intestines due to uncoordinated movements of the muscles of the digestive tract). This leads to constipation and diarrhea.

Some affected individuals may even show mild neurological impairment such as learning disability, impaired intellectual development, and autism (a developmental disorder that affects the social skills of the patient, like how the patient interacts with his surroundings).

How to Diagnose Pseudohypertrophic Myopathy?

A complete physical examination by the physician includes an assessment of the nervous system, heart, lungs, and muscles. The physician will prescribe the following tests to detect any abnormality in the body -

1. Electromyography (EMG) - This test is carried out to assess the functioning between the nerves and muscles. A small needle (electrode) is inserted in the affected muscles. This will enable the doctor to check the amount of electrical conduction at the muscles when nerve impulse is generated. This test will help differentiate muscular dystrophy from other neuromuscular disorders with similar symptoms. The doctor may also conduct nerve conduction studies to check how fast an electrical impulse travels through the nerve. A slow electrical response in the muscles indicates muscular dystrophy.

2. Serum CPK (Creatinine Phosphokinase) - A blood test will reveal elevated creatinine kinase levels in the serum. Creatinine kinase is secreted into the blood when there is a deterioration of muscle fibers. It is also secreted when there is inflammation in the muscles.

3. Genetic Testing - It identifies the genes, chromosomes, and proteins present in the genes. A blood test is routinely performed to conduct genetic testing, but muscle and skin biopsies can also be carried out. Genetic testing confirms the diagnosis of muscular dystrophy in a patient.

4. Muscle Biopsy - If genetic testing fails to identify the type of muscular dystrophy, muscle biopsy is recommended. This procedure is performed under anesthesia. The surgeon removes a small piece of the affected muscle and examines it under the microscope. This test can distinguish muscular dystrophy from other inflammatory disorders of the muscle.

What Is the Treatment of Pseudohypertrophic Myopathy?

The treatment of pseudohypertrophic myopathy comprises the management of symptoms to improve the quality of life. The following therapies may be useful in slowing down the progression of this disease -

1. Steroid medications slow down the loss of muscle strength.

2. Orthopedic appliances like wheelchairs may be useful for individuals who cannot walk.

3. Patients are encouraged to carry out physical activities to help their muscle strength and keep functioning. Inactivity or bedrest will worsen the condition of the muscles.

4. Medications are also prescribed to patients with heart problems.

5. Vitamin supplements such as fish oil capsules, vitamin E oil supplements, and green tea extracts may help nourish the body.

Conclusion:

Pseudohypertrophic myopathy is a highly debilitating disorder. Mutations in the genes responsible for protein production cause dysfunction of the muscle fibers. Stem cell therapy and gene therapy may be used to treat pseudohypertrophic myopathy. This disease is highly progressive, with worsening symptoms over time. Patients experience decreased mobility and a decreased ability to care for themselves. Patients may lead a normal life span but require medical assistance and medications to carry out daily tasks.