Myotonic dystrophy of Steinert

The myotonic dystrophy of Steinert or disease of Steinert is a Genetic disease reaching several bodies: the Skeleton, the smooth muscles, the eye, the Heart, the System endocrinien and the central Nervous system.

The signs of this disease are varied active from the average shape with low register. Three types of form are described but whose limits are not always clear: average, traditional and congenital.

  • the average form is characterized by a cataract and a moderate myotonie. The life expectancy is normal.
  • the traditional form is characterized by a generalized muscular weakness and a generalized myotonie, a cataract and Troubles of cardiac conduction. The adult can lose his autonomy and the life expectancy is reduced.
  • the congenital form with a muscular Hypotonia, often associated with a respiratory Insufficiency with early death. The Backwardness is frequent in this form.

The change is a Expansion of a triplet CTG of the Gène DMPK. This triplet is répètè more than 37 times at the people reached.

Aures names

  • dystrophic Myotonie of type 1
  • myotonic Dystrophy of type 1

Etiology

Change of the gene DMPK (for Dystrophy Myotonic Protein Kinase) located on the Locus q13-2 Chromosome 19 coding the Myotonine, a Protein dependant Kinase camp, whose precise role is unknown. The change in question is an expansion of the triplet CTG of which the number exceeds 37 at the people reached. When the number of repetition is higher than 50, the disease always appears. In the congenital form, the expansion of the triplet reaches several thousands.

Prevalence & incidence

The Prévalence of this disease is of 1 out of 100.000 to Japan and 1 out of 10.000 in Iceland. The world prevalence of this disease is of 1 out of 20.000.

Description of the disease

Diagnosis

  • the presumption of the diagnosis rests on the association of varied clinical signs (cataract, baldness, disorders muscular and cardiac…). The myotonie is the slow relaxation of the muscular contraction (hand which remains tight after a handshake, for example).
  • the certainty of the diagnosis is obtained by a technique of molecular biology, with a blood sample. The assent of the taken person is essential. The technique of TP- PCR is used and is enough to eliminate the healthy subjects (number of CTG lower than 37), hétérozygotes for the number of repetitions of triplet CTG on gene DMPK (the two alleles comprise less than 37 repetitions). At the healthy homozygotes and the hétérozygotes with expansion (they have an allele with less than 37 repetitions, and an allele with more than 37, and generally more than 50 CTG), one carries out a checking by Southern blot. The hétérozygotes with expansion are reached myotonic Dystrophy of Steinert.
  • the presence of a case of Dystrophy of Steinert within a family must start a family investigation. There still, the genetic investigation is not possible that with the agreement clarifies taken people.

Differential

Sources

  • myotonic Dystrophy of Steinert AFM
  • Online Mendelian Inheritance in Man, OMIM (TM). Johns Hopkins University, Baltimore, MANDELEVIUM. MIM Number: 160900 * Thomas D Bird, Standard Myotonic Dystrophy 1 In: GeneReviews At GeneTests: Medical Genetics Information Resource (database online). Copyright, University off Washington, Seattle. 1997-2005.
  • Article on Orpha.net of Dr. Alexandre Moerman and Professor Sylvie Manouvrier

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