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Childhood-onset Steinert myotonic dystrophy(Childhood-onset Steinert myotonic dystrophy)

来源:百科 / 时间: 2024-11-24

Childhood-onset Steinert myotonic dystrophy, also known as Childhood-onset myotonic dystrophy type 1 (DM1), is a rare genetic disorder that primarily affects the muscles and various other body systems. It is characterized by delayed muscle relaxation (myotonia), muscle weakness, and a wide range of systemic manifestations. This form of the disease typically presents in childhood or adolescence, distinguishing it from the more common adult-onset form.

疾病机制

Childhood-onset Steinert myotonic dystrophy type 1 (DM1) is caused by an expansion of a trinucleotide repeat (CTG) in the DMPK gene on chromosome 19. The repeat expansion leads to the production of an abnormally long RNA transcript, which interferes with the normal function of the gene and causes a toxic gain of function. This results in the misregulation of various cellular processes, including RNA splicing, protein synthesis, and cell signaling, ultimately leading to the characteristic features of the disease.

临床表现

The clinical manifestations of Childhood-onset DM1 are diverse and can affect multiple organ systems. Common features include:

  • Muscle Weakness and Myotonia: Delayed muscle relaxation and progressive muscle weakness, particularly in the face, neck, and distal muscles.
  • Cardiac Involvement: Arrhythmias, conduction abnormalities, and cardiomyopathy.
  • Endocrine Dysfunction: Diabetes mellitus, hypogonadism, and growth hormone deficiency.
  • Cognitive and Behavioral Issues: Intellectual disability, learning difficulties, and behavioral problems.
  • Pulmonary Involvement: Respiratory muscle weakness leading to respiratory insufficiency.
  • Gastrointestinal Issues: Delayed gastric emptying and constipation.

诊断

Diagnosis of Childhood-onset DM1 is based on clinical evaluation, family history, and genetic testing. Key diagnostic criteria include:

  • Clinical Features: Presence of myotonia, muscle weakness, and other systemic manifestations.
  • Family History: Positive family history of myotonic dystrophy.
  • Genetic Testing: Detection of a CTG repeat expansion in the DMPK gene. The number of repeats typically ranges from 100 to over 1,000, with higher repeat numbers correlating with more severe disease.

遗传咨询

Childhood-onset DM1 follows an autosomal dominant inheritance pattern, meaning that a single copy of the mutated gene is sufficient to cause the disease. Genetic counseling is essential for affected families to understand the inheritance risk and to provide guidance on prenatal testing and reproductive options. Key points include:

  • Inheritance Risk: Each child of an affected parent has a 50% chance of inheriting the mutation.
  • Prenatal Testing: Available through chorionic villus sampling or amniocentesis, allowing for the detection of the CTG repeat expansion.
  • Reproductive Options: Discussions on preimplantation genetic diagnosis (PGD) for families at high risk.

预后

The prognosis for Childhood-onset DM1 varies depending on the severity of the disease and the presence of complications. Generally, the disease is progressive, and life expectancy may be reduced compared to the general population. Early intervention and multidisciplinary management can improve quality of life and help manage symptoms. Regular monitoring for cardiac, respiratory, and endocrine complications is crucial for long-term care.

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