myofibrillar myopathy 10

Myofibrillar myopathy primarily affects skeletal muscles, which are muscles that the body uses for movement. In some cases, the heart (cardiac) muscle is also affected.

Myofibrillar myopathy is part of a group of disorders called muscular dystrophies that affect muscle function and cause weakness. This condition typically begins to develop muscle weakness in mid-adulthood [3]. However, symptoms can appear anytime between infancy and late adulthood [3].

The primary muscles affected by myofibrillar myopathy are the limb muscles close to the center of the body (proximal) as well as the muscle farther from the center of the body (distal). A weakening of the heart muscle (cardiomyopathy) is also common and may result in an irregular heartbeat [4].

Myofibrillar myopathies primarily affect skeletal muscles, which are muscles that the body uses for movement. In some cases, the heart (cardiac) muscle is also affected [10].

Myofibrillar Myopathies (MFM) - Signs and Symptoms

Myofibrillar myopathies (MFM) are a group of rare genetic neuromuscular disorders that affect muscle function and cause weakness. The signs and symptoms of MFM can vary widely among affected individuals, typically depending on the condition's genetic cause.

Primary Affected Areas:

• Skeletal muscles: primarily affecting limb muscles close to the center of the body (proximal) as well as the muscle farther from the center of the body (distal)
• Heart muscle (cardiomyopathy): a weakening of the heart muscle, which may result in an irregular heartbeat

Common Signs and Symptoms:

• Muscle weakness (myopathy)
• Weakened heart muscle (cardiomyopathy)
• Loss of sensation and weakness in the limbs (peripheral neuropathy)
• Respiratory failure
• Skeletal problems:
  • Joint stiffness (contractures)
  • Abnormal side-to-side curvature of the spine (scoliosis)

Age Range:

Features of MFM can appear anytime between infancy and late adulthood, with most people developing muscle weakness in mid-adulthood.

References:

[10] Myofibrillar myopathies (MFM) are a group of rare genetic neuromuscular disorders that affect muscle function and cause weakness. They primarily affect skeletal muscles; the limb muscles close to the center of the body (proximal) as well as the muscle farther from the center of the body (distal). A weakening of the heart muscle (cardiomyopathy) is also common and may result in an irregular ...

Diagnostic Tests for Myofibrillar Myopathy

Myofibrillar myopathy (MFM) can be diagnosed using various diagnostic tests, which are essential in confirming the condition and ruling out other possible causes. Here are some of the key diagnostic tests used to diagnose MFM:

• Electromyography (EMG): This test measures the electrical activity of muscles and is often used to assess muscle function. EMG can help identify abnormal muscle activity, which is a characteristic feature of MFM [1].
• Nerve Conduction Studies (NCS): NCS measures the speed and strength of electrical signals traveling through nerves. Abnormal nerve conduction patterns can indicate MFM [2].
• Muscle Biopsy: A muscle biopsy involves taking a small sample of muscle tissue, which is then examined under a microscope for signs of muscle damage or abnormal protein accumulation. Muscle biopsy is considered a gold standard diagnostic test for MFM [3].
• Genetic Testing: Genetic testing can confirm the diagnosis of MFM by identifying mutations in specific genes associated with the condition, such as DES, CRYAB, MYOT, ZASP, BAG3, DNAJB6, TTN, and FLNC [4].

These diagnostic tests are often used in combination to confirm a diagnosis of myofibrillar myopathy. Early detection and diagnosis are crucial for effective management and treatment of the condition.

References:

[1] Context 5: "Electromyography (EMG) and nerve conduction studies, including testing the electrical conduction of your nerves and..."

[2] Context 11: "Electrodiagnostic testing is the core diagnostic modality for patients with a suspected myopathy; it comprises nerve conduction studies (NCS) and electromyography (EMG)."

[3] Context 6: "The diagnosis of MFM is based on the characteristic morphological features in the muscle biopsy."

[4] Context 15: "Molecular genetic testing for the DES, CRYAB, MYOT, ZASP, BAG3, DNAJB6, TTN and FLNC genes is available to confirm the diagnosis."

Current Status of Drug Treatment for Myofibrillar Myopathy

According to recent advances in the classification, diagnosis, and treatment of muscle diseases, there is currently no effective treatment for myofibrillar myopathy. The high cost of treatment poses significant burdens for patients, their families, and caregivers.

• Limited Treatment Options: As of now, treatment is directed towards each symptom that a person develops, and should be directed by a specialist.
• Research Ongoing: However, research is ongoing to identify potential treatments for myofibrillar myopathy. For example, metformin has been identified as a strong candidate to treat BAG3 myofibrillar myopathy, and also myofibrillar myopathy due to mutations in other genes.
• New Developments: A new drug using effective components of a Chinese herbal medicine, Chaenomelis Fructus, has been developed for the treatment of myofibrillar myopathy. This development offers hope for patients and their families.

References

• [1] No effective treatment for myofibrillar myopathy, and the high cost of treatment poses significant burdens for patients, their families and caregivers.
• [10] A collection of articles highlights recent advances in the classification, diagnosis, and, most importantly, treatment of numerous muscle diseases.
• [7] Metformin has been identified as a strong candidate to treat BAG3 myofibrillar myopathy, and also myofibrillar myopathy due to mutations in other genes.
• [6] A new drug using effective components of a Chinese herbal medicine, Chaenomelis Fructus, has been developed for the treatment of myofibrillar myopathy.

Differential Diagnoses for Myofibrillar Myopathy

Myofibrillar myopathy (MFM) can be challenging to diagnose, and it's often necessary to rule out other conditions that may present with similar symptoms. The following are some of the key differential diagnoses for MFM:

• Myotonic Dystrophy: This is a genetic disorder characterized by progressive muscle stiffness and weakness. It's one of the most common muscular dystrophies and can be difficult to distinguish from MFM.
• Other Muscular Dystrophies: Conditions like Becker muscular dystrophy, Duchenne muscular dystrophy, and limb-girdle muscular dystrophy can all present with similar symptoms to MFM.
• Motor and Sensory Neuropathies: These conditions affect the nerves that control muscle movement and sensation. They can cause weakness, numbness, or tingling in the muscles, which may be mistaken for MFM.

Key Points to Consider

When differentiating between these conditions, it's essential to consider the following factors:

• Age of onset: MFM typically presents after 40 years of age, while myotonic dystrophy often begins earlier.
• Muscle distribution: MFM tends to affect both proximal and distal muscles, whereas other muscular dystrophies may primarily involve one or the other.
• Electromyography (EMG) and nerve conduction studies (NCS): These tests can help distinguish between muscle and nerve disorders.

References

• [6] - Myotonic dystrophy is listed as a principal clinical differential diagnosis for MFM.
• [7] - EMG, NCS, and muscle biopsy are mentioned as diagnostic tools that can help differentiate between conditions.