myofibrillar myopathy 8

Myofibrillar Myopathy: A Rare Muscle Disorder

Myofibrillar myopathy is a rare muscle disorder that affects the skeletal muscles, which are responsible for movement, and in some cases, the heart muscle. This condition is characterized by slowly progressive weakness that can involve both proximal (closer to the center of the body) and distal (further from the center of the body) muscles.

Key Features:

• Slowly progressive muscle weakness
• Involvement of both proximal and distal muscles
• Distal muscle weakness is more pronounced in about 25% of individuals
• Sensory symptoms, muscle stiffness, aching, or cramps may occur in some cases

Muscle Affected: Myofibrillar myopathy primarily affects skeletal muscles, which are responsible for movement. In some cases, the heart (cardiac) muscle is also affected.

Age of Onset: Symptoms can appear anytime between infancy and late adulthood, with most people developing muscle weakness in mid-adulthood.

References:

• [8] Myofibrillar myopathy is part of a group of disorders called muscular dystrophies that affect muscle function and cause weakness.
• [10] Description. Myofibrillar myopathy is part of a group of disorders called muscular dystrophies that affect muscle function and cause weakness.

Common Signs and Symptoms of Myofibrillar Myopathy

Myofibrillar myopathy (MFM) is a rare genetic disorder that affects the skeletal muscles, leading to progressive muscle weakness. The signs and symptoms of MFM can vary from person to person but often include:

• Muscle Weakness: A slowly progressive muscle weakness that can involve skeletal muscles, making it difficult to perform daily activities.
• Cardiomyopathy: A weakened heart muscle (cardiomyopathy) that can lead to heart failure.
• Muscle Pain (Myalgia): Muscle pain or tenderness, especially after physical activity.
• Loss of Sensation: Loss of sensation in the limbs or other areas.
• Peripheral Neuropathy: Pain and tingling in the limbs due to nerve damage.

In some cases, MFM can also cause:

• Intermittent Tying Up: Episodes of muscle pain, stiffness, and weakness in horses, particularly those competing in endurance events.
• Muscle Fibrosis: Increased fibrosis (scarring) in the muscles, which can lead to further muscle weakness.

It's essential to note that these symptoms can vary in severity and may not be present in all individuals with MFM. If you or someone you know is experiencing any of these symptoms, it's crucial to consult a healthcare professional for proper diagnosis and treatment.

References:

• [1] Muscle biopsies from MFM patients show primary degeneration of the muscle fibers, increased fibrosis, as well as necrotic and regenerating fibers. (Source: [4])
• [2-3] Other symptoms that can be associated with MFM include pain and tingling in the limbs (peripheral neuropathy) or an enlarged and weakened heart (cardiomyopathy). (Sources: [3], [6])
• [5] Myopathy refers to diseases that affect skeletal muscles (muscles that connect to your bones). These diseases attack muscle fibers, making your muscles weak. (Source: [5])

Myofibrillar myopathy (MFM) can be diagnosed using several diagnostic tests, including:

• Muscle biopsy: This is a key test for diagnosing MFM, as it allows for the examination of muscle tissue under a microscope. In trichrome-stained sections of diseased muscle, abnormal fibers harbor an admixture of normal and abnormal myofibrils [2].
• Electromyography (EMG) and nerve conduction studies: These tests measure the electrical activity of muscles and nerves, which can be affected in MFM.
• Blood tests: Enzyme tests, such as creatine kinase (CK), can detect damaged muscles releasing enzymes into the blood [8].
• Genetic testing: This can confirm the diagnosis of MFM by identifying specific genetic mutations associated with the condition [7].
• Heart-monitoring tests: These may be performed to assess cardiac function in individuals with MFM, as some people with this condition may experience heart problems.
• The Invitae Comprehensive Myopathy Panel: This panel analyzes genes associated with inherited myopathies, including those that can cause MFM.

These diagnostic tests are used in combination to confirm the diagnosis of myofibrillar myopathy.

Current Research on Drug Treatment for Myofibrillar Myopathy

According to recent studies, metformin has been identified as a strong candidate to treat BAG3 myofibrillar myopathy [8]. This is because metformin stimulates autophagy, which can help reduce protein aggregation and prevent fiber disintegration in muscle cells [9].

Additionally, research suggests that repurposing metformin provides a promising therapy for BAG3 myopathy, as it has been shown to reduce protein aggregation and improve muscle function [7]. This is an exciting development in the treatment of myofibrillar myopathy, as it may offer a new avenue for managing this condition.

It's worth noting that while these findings are promising, more research is needed to fully understand the potential benefits and limitations of metformin as a treatment for myofibrillar myopathy. However, these studies do provide hope for patients and families affected by this rare disease.

References:

[7] Ruparelia AA (2021) - Our data collectively demonstrated that the FDA-approved, autophagy stimulating drug, metformin reduced protein aggregation, prevented fiber disintegration, ...

[8] Oct 14, 2020 - "We have identified metformin as a strong candidate to treat BAG3 myofibrillar myopathy, and also myofibrillar myopathy due to mutations in ...

[9] by AA Ruparelia · 2021 · Cited by 36 — Our study suggests treatment of BAG3 myofibrillar myopathy would be achieved through stimulation of autophagy, removing protein aggregates and overcoming ...

Differential Diagnoses for Myofibrillar Myopathy

Myofibrillar myopathy (MFM) can be challenging to diagnose, and it's often confused with other muscular dystrophies. Here are some key differential diagnoses to consider:

• Myotonic Dystrophy: This is a genetic disorder that affects muscle tone, leading to stiffness and wasting of muscles. It's one of the most common differential diagnoses for MFM.
• Motor and Sensory Neuropathies: These conditions affect the nerves that control muscle movement and sensation. They can cause similar symptoms to MFM, such as weakness and wasting of muscles.
• Muscular Dystrophies: Other types of muscular dystrophy, such as Duchenne muscular dystrophy and Becker muscular dystrophy, can also be considered in the differential diagnosis for MFM.

These conditions often present with similar symptoms to MFM, making it essential to perform a thorough clinical evaluation, electromyography, nerve conduction studies, and muscle biopsy to establish an accurate diagnosis.