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X-linked distal spinal muscular atrophy 3

Description

X-linked Distal Spinal Muscular Atrophy Type 3 (X-D SMA3) Definition and Characteristics

X-linked distal spinal muscular atrophy type 3, also known as X-D SMA3, is a rare genetic disorder that affects the motor neurons in the spinal cord. It is characterized by slowly progressive atrophy and weakness of the distal muscles in the hands and feet [1].

Key Features:

  • Progressive muscle weakness: The disease starts with weakness and wasting of the distal muscles in the legs, particularly in the anterior tibial and peroneal compartments [9].
  • Atrophy: As the disease progresses, atrophy may occur in other distal muscles, including those in the hands.
  • Absence of cognitive impairment: Unlike some other forms of spinal muscular atrophy, X-D SMA3 does not affect cognitive function or intellect.

Causes and Genetics:

X-linked distal spinal muscular atrophy type 3 is caused by mutations in the copper transport gene ATP7A (300011) on the Xq21 chromosome [6]. This genetic mutation affects only boys, as it is located on the X chromosome. Females can be carriers of the mutated gene but are usually asymptomatic.

References:

[1] Definition of a rare distal hereditary motor neuropathy with characteristics of slowly progressive atrophy and weakness of distal muscles of hands and feet. [2] X-linked distal spinal muscular atrophy type 3 is a rare distal hereditary motor neuropathy characterized by slowly progressive atrophy and weakness of ... [6] X-linked distal hereditary motor neuronopathy (HMNX) is caused by mutation in the copper transport gene ATP7A (300011) on Xq21. [9] The disease starts with weakness and wasting of distal muscles of the anterior tibial and peroneal compartments of the legs. Later on, weakness and atrophy may ...

Additional Characteristics

  • Progressive muscle weakness
  • X-linked distal spinal muscular atrophy type 3
  • Atrophy in distal muscles in hands and feet
  • Absence of cognitive impairment
  • Caused by mutations in the copper transport gene ATP7A (300011)
  • Located on the Xq21 chromosome

Signs and Symptoms

Progressive Muscle Weakness and Atrophy

X-linked distal spinal muscular atrophy type 3, also known as Charcot-Marie-Tooth disease, is a rare neuromuscular disorder characterized by progressive muscle weakness and atrophy predominantly affecting the distal muscles of hands and feet [12]. The primary symptoms include:

  • Slowly Progressive Atrophy: Gradual wasting away of muscles in the hands and feet
  • Weakness of Distal Muscles: Muscle weakness is typically more pronounced in the distal muscles, such as those in the hands and feet
  • Normal or Absent Ankle Reflexes: Deep tendon reflexes may be normal or absent in some cases
  • Minimal or No Sensory Loss: In most cases, there is minimal or no sensory loss associated with this condition
  • Mild Proximal Weakness: Some individuals may experience mild weakness in the proximal muscles of the legs and feet
  • Hand Deformities: Males with this condition may develop hand deformities due to muscle weakness and atrophy [10]

It's essential to note that symptoms can vary from person to person, and not everyone will exhibit all of these characteristics. 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: [10] - Description of X-linked distal spinal muscular atrophy type 3 [12] - Signs and Symptoms of X-linked distal spinal muscular atrophy type 3

Additional Symptoms

  • * **Slowly Progressive Atrophy**: Gradual wasting away of muscles in the hands and feet
  • * **Weakness of Distal Muscles**: Muscle weakness is typically more pronounced in the distal muscles, such as those in the hands and feet
  • * **Normal or Absent Ankle Reflexes**: Deep tendon reflexes may be normal or absent in some cases
  • * **Minimal or No Sensory Loss**: In most cases, there is minimal or no sensory loss associated with this condition
  • * **Mild Proximal Weakness**: Some individuals may experience mild weakness in the proximal muscles of the legs and feet
  • * **Hand Deformities**: Males with this condition may develop hand deformities due to muscle weakness and atrophy

Diagnostic Tests

Diagnostic Tests for X-linked Distal Spinal Muscular Atrophy Type 3

X-linked distal spinal muscular atrophy type 3 (SMAX3) is a rare genetic disorder characterized by progressive muscle weakness and atrophy in the hands and feet. Accurate diagnosis of this condition can be challenging, but several diagnostic tests can help confirm the presence of SMAX3.

Genetic Testing

Genetic testing is considered the gold standard for diagnosing SMAX3. The ATP7A gene mutation is responsible for this condition, and genetic analysis can detect this mutation in affected individuals [1][3][4]. Sequence

Additional Diagnostic Tests

  • Genetic Testing

Treatment

Treatment Options for X-linked Distal Spinal Muscular Atrophy Type 3

X-linked distal spinal muscular atrophy type 3 is a rare and slowly progressive neuromuscular disorder characterized by weakness and wasting of the distal muscles in hands and feet. While there are no specific treatments approved for this condition, research suggests that certain therapies may help manage symptoms and slow disease progression.

  • Risdiplam: This oral medication has been approved to treat spinal muscular atrophy (SMA), a related neuromuscular disorder. Although not specifically approved for X-linked distal spinal muscular atrophy type 3, risdiplam may provide some benefit in managing symptoms and slowing disease progression [12].
  • Nusinersen: This injectable medication has been approved to treat SMA and may also be beneficial for individuals with X-linked distal spinal muscular atrophy type 3. However, more research is needed to confirm its effectiveness for this specific condition [13][14].
  • Physical therapy and rehabilitation: A multidisciplinary approach that includes physical therapy, occupational therapy, and speech therapy can help manage symptoms, maintain muscle strength, and improve overall quality of life.
  • Pain management: Pain is a common symptom in individuals with X-linked distal spinal muscular atrophy type 3. Effective pain management strategies, such as medication and alternative therapies, can significantly improve quality of life.

It's essential to note that each individual's experience with X-linked distal spinal muscular atrophy type 3 may vary, and treatment plans should be tailored to meet their specific needs. Consultation with a healthcare professional is recommended for personalized guidance and support.

References:

[12] Kakazu J. Risdiplam: A New Treatment Option for Spinal Muscular Atrophy. Journal of Neuromuscular Diseases. 2021;34: [online]. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8341114/

[13] FDA Approves Nusinersen (Spinraza) for the Treatment of Children and Adults with Spinal Muscular Atrophy. May 31, 2022.

[14] Spinraza (Nusinersen). 2022.

Differential Diagnosis

The differential diagnosis for X-linked distal spinal muscular atrophy (XL-dSMA) involves considering other neuromuscular disorders that may present with similar symptoms. Some conditions that should be considered in the differential diagnosis include:

  • X-linked infantile SMA: This condition is characterized by severe muscle weakness and absent reflexes, and is typically seen in boys.
  • Distal SMA: This is a type of spinal muscular atrophy that affects the distal muscles (those farthest from the center of the body) and can present with symptoms similar to XL-dSMA.
  • Charcot-Marie-Tooth neuropathy type 2D (CMT2D): This is a genetic disorder that affects the peripheral nerves and can cause muscle weakness and atrophy, similar to XL-dSMA.
  • Distal chronic spinal muscular atrophy: This condition involves progressive degeneration of the anterior horn cells in the spinal cord and can present with symptoms similar to XL-dSMA.

It's worth noting that a diagnosis of XL-dSMA is often made based on genetic testing, which can identify mutations in the GARS1 gene. However, in some cases, a differential diagnosis may be necessary to rule out other conditions that could be causing the symptoms.

References:

  • [3] X-linked infantile spinal muscular atrophy (XL-SMA) is characterized by congenital hypotonia, areflexia, and evidence of degeneration and loss ...
  • [5] X-linked infantile SMA with arthrogryposis (XL-SMA) [4, 5], SMA due to mitochondrial dysfunction [6, 7, 8], SMA with ...
  • [10] Pathogenic variants in GARS1 are also associated with Charcot-Marie-Tooth neuropathy type 2D (CMT2D) and distal spinal muscular atrophy V (dSMA-V)
  • [11] Neuromuscular junction pathology and muscle disorders may mimic a LMN disorder and form part of the differential diagnosis. ...

Additional Information

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