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myotonic dystrophy type 1

MIM.160900 19q13.2-q13.3

Thursday 27 January 2005

Definition: Myotonic dystrophy type 1 is an autosomal dominant disorder characterized by myotonia, muscular dystrophy, cataracts, hypogonadism, frontal balding, and ECG changes.

Etiology

- Myotonic dystrophy type 1 (Steinert disease) is caused by CTG triplet expansion in the dystrophia myotonica protein kinase gene (DMPK) (MIM.605377) at 19q13.2-q13.3.

  • Normal - 5 to 27 copies of repeat
  • Affected, Mild - 50-80 repeats
  • Adult Onset - 100-500 repeats
  • Congenital - 500-2,000 repeats
  • possible negative repeat expansion (reverse anticipation)

Synopsis

- cataract
- swallowing and speech disability
- poor feeding (congenital form)
- atrial arrhythmias
- cardiac conduction block
- cholelithiasis
- recurrent intestinal pseudoobstruction
- hypogonadism
- testicular atrophy
- uncoordinated uterine contraction
- frontal balding (male pattern baldness)

- muscular anomalies

  • myotonia
  • weakness
  • wasting, especially temporal, neck, and facial
  • respiratory distress (congenital form)
  • bilateral facial weakness (congenital form)
  • absence of myotonia in infancy (congenital form)

- multiple pilomatricomas
- cerebrospinal anomalies

  • mild cognitive deterioration in adults
  • swallowing and speech disability
  • hypotonia (congenital form)
  • severe mental retardation (congenital form)

- congenital forms

  • reduced fetal movements (congenital form)
  • polyhydramnios

Videos

- muscular dystrophy by Washington Deceit

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References

- Effect of unexpected sequence interruptions to conventional PCR and repeat primed PCR in myotonic dystrophy type 1 testing. Radvansky J, Ficek A, Minarik G, Palffy R, Kadasi L. Diagn Mol Pathol. 2011 Mar;20(1):48-51. PMID: 21326039