Muscular myotonic

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). 

Enteric Myopathies. The familial types include the dominant type 1 [150], the recessive type 2 with ophthalmoplegia [151] and the recessive type 3 [116]. The sporadic types include muscular dystrophies [152] including myotonic dystrophy [153] and Duchenne s dystrophy. Dysmotility has been associated with all these diseases. 

Pain, muscular weakness, cramps and ease of fatigue are the most usual symptoms of muscular disease. In most cases, it is diseases of the vascular or nervous system or problems with the processes providing energy within the muscle that are responsible for clinical problems with muscles. Other clinical problems include the muscular dystrophies, myotonic disorders, inflammatory myopathies and disorders of neuromuscular transmission (see Walton, 1996). The best known is Duchenne muscular dystrophy. 

Myotonic dystrophy is a generalized adult-onset disorder with muscular spasms, weakness, and many other symptoms.11 It is one of the triple-repeat diseases (Table 26-4). The affected gene encodes a protein kinase of unknown function. The corresponding mRNA transcript has -2400 nucleotides. The gene has a CTG repeat (CTG) near the 3 -end with n< 30 normally. For persons with the mildest cases of myotonic dystrophy n may be over 50 while in severe cases it may be as high as 2000. As in other triple-repeat diseases the repeat number tends to increase in successive generations of people as does the severity of the diseased... 

The local injection of 0.1 to 2% procaine or other anesthetics blocks the centripetal proprioceptive impulses and thereby relaxes muscular tonus, normal and abnormal, such as spasmodic torticollis. It effects almost instantaneous relief of the pain, stiffness, malposition, and incapacity of fibrositis, lumbago, and acute sprains and fractures. The site of greatest tenderness may be infiltrated with 10 to 30 cc of 1 or 2% procaine hydrochloride. Injected systemically, it relaxes traumatic tetanus and removes decerebrate rigidity, so that spontaneous movements of the limbs and of the respiration return. Its curare action may also be concerned in this effect. It relaxes parkinsonian, but not myotonic, rigidity. 

Seznec, H., Agbulut, O., Sergeant, N., Savouret, C., Ghestem, A., Tabti, N., et al. (2001) Mice transgenic for the human myotonic dystrophy region with expanded CTG repeats display muscular and brain abnormalities. Hum Mol Genet 10, 2717-2726. 

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

FSHD is the third most common hereditary muscular dystrophy after Duchenne muscular dystrophy and myotonic dystrophy. As its name represents, the disease predominantly affects the face, the scapulae, and the proximal arm muscles. In... 

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). 

ShoU JS, Hughey MJ, Hrrschmann RA. Myotonic muscular dystrophy associated with ritodrine tocolysis. Am J Obstet Gynecol 1985 151(l) 83-6. 

W5. Walton, J. N., and Gardner-Medwin, D., Progressive muscular dystrophy and the myotonic disorders. In Disorders of Voluntary Muscle (J. N. Walton, ed.), pp. 455-499. Churchill, London, 1969. 

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. 

Pathogenic effects may be caused by mutant mRNA. In the case of myotonic dystrophy (MD, prevalence 1 in 7400 live buths), is the most common form of muscular dystrophy in adult humans and results from the expansion of a CTG repeat in the 3 untranslated region of the DMPK gene. The mutant DMPK mRNA contains an expanded CUG repeat and is retained in the nucleus. An untranslated CUG repeat was expressed in an unrelated mRNA... 

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