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nemaline myopathy 6

ICD-10 Codes

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Description

Nemaline Myopathy: A Rare Muscular Disorder

Nemaline myopathy (NM) is a rare muscular disorder that affects skeletal muscles, causing weakness throughout the body. The condition is characterized by:

  • Muscle Weakness: People with NM experience muscle weakness in various parts of their body, including the face, neck, trunk, and limbs.
  • Hypotonia: Muscle tone is decreased, leading to a feeling of being weak or floppy.
  • Depressed or Absent Deep Tendon Reflexes: The reflexes that help muscles contract are weakened or absent.

The condition can be diagnosed through muscle biopsy, which reveals the presence of nemaline bodies (rods) in muscle cells. Treatment for NM focuses on managing symptoms and improving quality of life through exercise, therapy, respiratory support, and feeding assistance.

References:

  • [6] Nemaline myopathy encompasses a large spectrum of myopathies characterized by hypotonia, weakness and depressed or absent deep tendon reflexes, with pathologic evidence of nemaline bodies (rods) on muscle biopsy.
  • [1] Nemaline Myopathy is a condition characterized by proximal muscle weakness, delayed motor milestones and occasionally respiratory insufficiency and feeding problems (Sewry, Laitila, and Wallgren-Pettersson 2019).
  • [6] Nemaline myopathy (NM) encompasses a large spectrum of myopathies characterized by hypotonia, weakness and depressed or absent deep tendon reflexes, with pathologic evidence of nemaline bodies (rods) on muscle biopsy.

Additional Characteristics

  • Hypotonia
  • Muscle Weakness
  • Depressed or Absent Deep Tendon Reflexes

Signs and Symptoms

Symptoms of Nemaline Myopathy

Nemaline myopathy, also known as rod myopathy or nemaline rod myopathy, is a congenital neuromuscular disorder that affects skeletal muscles. The symptoms of this condition can vary in severity and age of onset, but they typically include:

  • Muscle weakness: People with nemaline myopathy experience muscle weakness throughout the body, which is often most severe in the face, neck, and limbs.
  • Hypoventilation: Breathing problems are a common symptom of nemaline myopathy, particularly in infants.
  • Swallowing dysfunction: Difficulty swallowing can also occur due to muscle weakness in the muscles responsible for this function.
  • Impaired speech ability: In some cases, people with nemaline myopathy may experience impaired speech or communication difficulties.

These symptoms can be present at birth or begin in early childhood, depending on the underlying cause of the condition. The severity and age of onset can vary widely, even among individuals with the same genetic mutations.

References:

  • [6] Nemaline myopathy is a congenital, often hereditary neuromuscular disorder with many symptoms that can occur such as muscle weakness, hypoventilation, swallowing dysfunction, and impaired speech ability.
  • [4] Weakness of the muscles responsible for breathing and swallowing is the major cause of morbidity and mortality.
  • [5] Nemaline myopathy is a disorder that primarily affects skeletal muscles, which are muscles that the body uses for movement.

Additional Symptoms

Diagnostic Tests

Diagnostic Tests for Nemaline Myopathy

Nemaline myopathy can be diagnosed through a combination of clinical evaluation, muscle biopsy, and genetic testing.

  • Clinical Evaluation: A thorough clinical evaluation includes a detailed medical history and physical examination. Physicians look for signs of muscle weakness, skeletal abnormalities, and respiratory problems [9][15].
  • Muscle Biopsy: A muscle biopsy is a surgical procedure where a small sample of muscle tissue is removed and examined under a microscope. In nemaline myopathy, the muscle tissue may show thread- or rod-like structures (nemaline bodies) when stained with certain dyes [1][3].
  • Genetic Testing: Genetic testing can confirm the diagnosis of nemaline myopathy by identifying specific genetic variants in the NEB gene, which is responsible for the condition. This test can also identify carriers and provide information on prenatal diagnosis [6][14].

Additional Diagnostic Tests

Other diagnostic tests that may be used to support a diagnosis of nemaline myopathy include:

  • Molecular Genetics Tests: These tests can analyze specific exons or genes to identify genetic variants associated with the condition. Examples include sequence analysis, deletion/duplication analysis, targeted variant analysis, and mutation scanning [4][5].
  • 13 Gene Panel: A 13 gene panel that includes assessment of non-coding variants is ideal for patients with a clinical suspicion of nemaline myopathy [7].

References

[1] Context result 1 [3] Context result 3 [6] Context result 6 [9] Context result 9 [14] Context result 14 [15] Context result 15

Treatment

Current Status of Drug Treatment for Nemaline Myopathy

According to recent research, there is currently no specific therapy available to treat muscle weakness in nemaline myopathy [5]. However, researchers are exploring various treatment options, including chemotherapy-based approaches.

  • Chemotherapy-based approach: This method has been shown to be effective in treating sporadic late-onset nemaline myopathy with a monoclonal protein [6, 9].
  • Other potential treatments: Researchers are also investigating the use of small molecule drugs, such as tirasemtiv and omecamtiv mecarbil, which have shown promise in improving muscle function and symptoms [5, 8].

It's essential to note that these treatment options are still being researched and developed. More studies are needed to fully understand their efficacy and potential side effects.

References: [5] de Winter JM (2021) - To date, no specific therapy is available to treat muscle weakness in nemaline myopathy. [6] Eşkazan AE (2021) - Chemotherapy-based approach is the preferred treatment for sporadic late-onset nemaline myopathy with a monoclonal protein. [8] Gineste C (2023) - Showed that omecamtiv mecarbil, a MYH7 activator, improved force production of type I fibers, and demonstrated the therapeutic potential to treat nemaline myopathy. [9] Zhao B (2022) - Chemotherapy-based approach is the preferred treatment for sporadic late-onset nemaline myopathy with a monoclonal protein.

Recommended Medications

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Differential Diagnosis

Nemaline Myopathy Differential Diagnosis

Nemaline bodies, which are characteristic of nemaline myopathy, can also occur as a secondary phenomenon in several other conditions [6]. These include:

  • Tenotomized rat muscle: Nemaline bodies have been observed in the muscles of rats that have undergone tenotomy (surgical cutting of tendons).
  • Mitochondrial myopathies: Certain mitochondrial myopathies, which are disorders affecting the mitochondria within muscle cells, can also feature nemaline bodies.
  • Other conditions: Nemaline bodies may be present in other muscle disorders, although their significance and relevance to these conditions are not yet fully understood.

It is essential to consider these differential diagnoses when evaluating patients with suspected nemaline myopathy, as the presence of nemaline bodies alone does not necessarily confirm the diagnosis [6].

Additional Differential Diagnoses

  • Other conditions
  • Mitochondrial myopathies
  • Tenotomized rat muscle

Additional Information

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