Myotonic syndrome

Muscular dystrophy itself, however, is strictly defined as a genetically determined degenerative primary myopathy (W4). The condition is progressive, painless, almost always widespread, and frequently disastrous to the sufferer. The three main clinical forms are now described, together with the myotonic syndrome, but omitting those rare varieties mentioned elsewhere (W4). 

Genetic Transmission— by autosomal dominant inheritance as the commonest form of the myotonic syndrome. 

Trinucleotide sequences that increase in number (microsateUite instability) can cause disease. The unstable p(CGG) repeat sequence is associated with the fragile X syndrome. Other trinucleotide repeats that undergo dynamic mutation (usually an increase) are associated with Huntington s chorea (CAG), myotonic dystrophy (CTG), spinobulbar muscular atrophy (CAG), and Kennedy s disease (CAG). 

Blindness (several forms) Deafness (several forms) Marfan syndrome Achondroplasia Neurofibromatosis Myotonic dystrophy Tuberous sclerosis All others... 

The signs and symptoms of some genetic conditions tend to become more severe and appear at an earlier age as the disorder is passed from one generation to the next. This phenomenon is called anticipation. Anticipation is most often seen with certain genetic disorders of the nervous system, such as Huntington disease, myotonic dystrophy, and fragile X syndrome. 

Trinucleotide Repeat Expansion DNA region comprised of a variable number of repetitive, contiguous trinucleotide sequences. The presence of these regions is associated with diseases such as Fragile X Syndrome and myotonic dystrophy. Many chromosome fragile sites (chromosome fragility) contain expanded trinucleotide repeats, [nih]... 

Keywords Cerebellar ataxias Dentatorubral pallidoluysian atrophy Fragile X syndrome Friedreich ataxia Huntington disease Myotonic dystrophy Spinobulbar muscular atrophy Trinucleotide expansion diseases... 

Paradoxical contracture is most often associated with myotonia dystrophica and myotonia congenita. A myotonic reaction has also been reported in a patient with hjq)erkalemic periodic paralysis (60). Suxamethonium is therefore contraindicated in these conditions, even though normal responses are sometimes seen. Contracture has also been reported as a result of denervation in Pancoast s syndrome and after plexus injuries and, rarely, in patients with amyotrophic lateral sclerosis or multiple sclerosis (61-63). 

Other genetic syndromes sometimes associated with diabetes Down s syndrome Klinefelter s syndrome Turner s syndrome Wolfram s syndrome Friedreich s ataxia Huntington s chorea Laurence-Moon-Bieldel syndrome Myotonic dystrophy Porphyria... 

Trinucleotide repeat expansion Amplification from one generation to the next of three nucleotide repeats in the coding or noncoding regions of DNA. The mechanism may arise from DNA complimentary strand slippage. This is associated with fragile X syndrome and myotonic dystrophy. 

Many human diseases including cancer may involve mutations that cause defective splicing (Faustino and Cooper 2003). Some genes in which a mutation is known to cause defective splicing and human diseases include BRCA1 BRCA2, HGH, cystic fibrosis spinal muscular atrophy (SMA), myotonic dystrophy (MD), Wilms tumor suppressor associated with Frasier syndrome (WT1), and many more. 

Arikawa-Hirasawa E, Le AH, Nishino I, Nonaka I, Ho NC, Francomano CA, Govindraj P, Hassell JR, Devaney JM, Spranger J, Stevenson RE, lannaccone S, Dalakas MC, Yamada Y. Structural and functional mutations of the perlecan gene cause Schwartz-Jampel syndrome, with myotonic myopathy and chondrodysplasia. Am J Hum Genet 2002 70 1368-1375. 

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