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Muscular Dystrophies

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  1. Muscular Dystrophies

  2. What is Muscular Dystrophy?(MD) Muscular Dystrophy is a group ofgenetic disorders that cause progressive muscle weakness. MD is caused by a genetic mutation. The protein in the muscle is deformed which causes the patients muscle to deteriorate. MD is characterized by degeneration and regeneration of muscle fibers (in contrast with static or structural myopathies) progressive skeletal muscle weakness, defects in muscle proteins, and the death of muscle cells and tissue

  3. Symptoms Lack of coordination Muscle weakness Loss of mobility

  4. General Diagnostic Testing Creatine kinase : greatly elevated (50 times normal) Increased in DMD, BMD, polymyositis, and rhabdomyolysis Nonspecific if mildly elevated 2-3x normal Lower late in MD course due to severely reduced muscle mass Not helpful for carrier detection

  5. General Diagnostic Testing • Electromyography • Useful if diagnosis not clear (biopsy has mixed features) • Differentiates neuropathic vs. myopathic • Characteristic myotonic discharges in adults with myotonia – “dive bomber” sound • Perform after the CK

  6. General Diagnostic Testing • Muscle biopsy • Dystrophic changes include necrosis, degeneration, regeneration, fibrosis and fatty infiltration, sometimes mild inflammation • Specific diseases may have inflammation, intracellular vacuoles, rods, and other inclusions on biopsy

  7. General Diagnostic Testing • Biochemical muscle protein analysis • Useful for specific identified protein that is missing and many specific mutations may cause the same deficiency • Immunohistochemical protein staining • Western blot – quantitates percent of normal protein present

  8. General Diagnostic Testing • Genetic analysis • PCR for specific known defects • Southern blot for nucleotide repeats

  9. CLASSIFICATION X-linked muscular dystrophy Duchenne muscular dystrophy Becker muscular dystrophy Emery-Dreifuss syndrome Autosomal recessive muscular dystrophy Congenital muscular dystrophy Limb-girdle muscular dystrophy Autosomal dominant muscular dystrophy Limb-girdle muscular dystrophy Fascioscapulohumeral muscular dystrophy

  10. Differential Patterns of Initial Muscle Weakness in MD OPMD Oculopharyngeal MD Limb Girdle MD FSHD Facio- Scapulo- humeral Duchenne MD Emery-Dreifuss MD Congenital MD

  11. Duchenne Muscular Dystrophy (DMD) Presentation: 3-5 y/o with frequent falls, slow running, Prevalence of 1:3500 Etiology single gene defect (65% deletions in hot spot regions , 7-10% duplications, 25% point mutations, small deletions or insertions) 1/3 new mutation 2/3 family history Xp21.2 region absent dystrophin

  12. Duchenne Muscular Dystrophy(DMD)

  13. Duchenne Muscular Dystrophy(DMD) • Clinical Manifestations • Onset : age 3-6 years • Progressive weakness • Pseudohypertrophy of calf muscles • Spinal deformity • Cardiomyopathy • Respiratory • 30% mild to moderate MR

  14. Pseudohypertrhophy of calf muscle, • Tip toe gait • forward tilt of pelvis, compensatory lordosis

  15. Disappearance of lordosis while sitting


  17. Duchenne Muscular Dystrophy(DMD) • Natural History • Progress slowly and continuously • muscle weakness • lower --> upper extremities • unable to ambulate: 10 year (7-12) • death from pulmonary/ cardiac failure: 2-3rd decade

  18. Duchenne Muscular DystrophyDiagnosis Clinical Signs (Gower’s Sign) Family history (pedigree analysis) Increase CPK (200x) DNA mutation analysis (65%) or haplotype analysis) Myopathic change in EMGBx: m. degeneration Muscle biopsy and Immunoblotting: Absence dystrophin (if geneticist can’t find the mutation !!) Prenatal diagnosis is available

  19. Becker Muscular Dystrophy (BMD) Slowly progressive form with same gene affected as Duchenne MD Etiology single gene defect short arm X chromosome altered size & decreased amount of dystrophin Muscle biopsy immunostaining for dystrophin with patchy staining Disorder of function or decreased amount of dystrophin rather than absence of the protein

  20. DMD / BMD

  21. Emery-Dreifuss Muscular Dystrophy (EDMD) Presentation: This disorder is characterized by a triad Early contractures of the Achilles tendon, elbows and posterior cervical muscles Slowly progressive muscle wasting and weakness with a humeroperoneal distribution Cardiomyopathy arises , which usually presents as cardiac conduction defects. Genetics X-linked type affects emerin (STA gene at chromosome Xq28) Diagnose by protein analysis of leukocytes or skin fibroblasts DNA testing available AD affects lamin A or lamin C (chromosome 1q21)

  22. Congenital Muscular Dystrophy (CMD) Presentation: neonatal onset of severe weakness, delayed motor milestones, contractures Classification Merosin-negative Merosin-positive Neuronal migration Fukuyama Muscle eye-brain Wlaker-Warburg

  23. Limb Girdle Muscular Dystrophy (LGMD) Presentation: variable age of onset with weakness and wasting of the limb-girdle 15 genetically different types (genetical and clinical heterogenic) AD forms are rare but more less severe than AR forms Several of these disorders are associated with clinically significant cardiac involvment

  24. FascioScapuloHumeral Muscular Dystrophy (FSMD) Presentation: Facial and shoulder girdle are first affected muscle group Later foot extensors and pelvic girdle muscles become involved The heart is not implicated in most cases. mild high pitched hearing loss, retinal abnormalities, mental retardation in early onset Genetics/Testing Southern blot testing available (chromosome 4q35) for decrease in repeats normally present Muscle biopsy may show lymphocytic infiltrates

  25. Oculopharyngeal Muscular Dystrophy Presentation: mid-adult with ptosis, facial muscle weakness with difficulty swallowing, proximal muscle weakness, may have extraocular muscle weakness, more common in French-Canadian and Hispanic population Genetics Affects poly A binding protein 2 (PABP2) by expansion of a GCG repeat without anticipation seen – Southern blot (chromosome 14q11-13)

  26. Myotonic Dystrophy (DM) Presentation – adult with multiple systems affected Primarily distal and facial weakness Facial features: frontal balding in men, ptosis, low-set ears, hatchet jaw, dysarthria, swan neck, ^ shaped upper lip Myotonia: worse in cold weather, after age 20 Heart: conduction block – evaluate syncope

  27. Smooth muscle: constipation, care with swallowing, gallstones, problems with childbirth, BP lability • Brain: learning disabilities, increased sleep requirement • Ophthalmology: cataracts • Endocrine: insulin resistance, hypothyroidism, testicular atrophy

  28. Myotonic Dystrophy • Genetics • Myotonic dystrophy is caused by a triple nucleotide (triplet) expansion (CTG) in the noncoding region of the myotonin gene at chromosome 19q13.3. • The condition is characterized by extreme variability, anticipation and differential expansion in the maternal and paternal germline. • 4-37 repeats Normal • >50 repeats Affected

  29. Congenital: severe form initial respiratory distress after birth with ventilatory requirement or apnea, feeding difficulty, mental retardation, club feet, scoliosis, strabismus Myotonic Dystrophy (DM)

  30. Huntington Disease (HD) • Presentation • Mood Swings • Impaired cognitive functions • Chorea • Huntington’s Disease is an Autosomal Dominant“Tri-nucleotide Repeat” Disorder caused by a mutation of a gene on the 4th chromosome which is responsible for producing the protein Huntingtin, that creates excess copies of the CAG codon which genetically program the degeneration of the neurons of the brain. • Age of onset is found generally in adults around the age of 40 but varies based on the number of repeats. • The earliest onset of Huntington’s ever documented was a two year old boy who was found to have nearly 100 CAG repeats. • The symptoms of HD can also develop at 55 or later, in which case it is harder to recognize.

  31. Huntington Disease (HD) The number of CAG codons varies and so does the severity of the disease • >40 repeats you develop HD, children 50% chance of developing disease • 36-39 repeats “Grey Zone” May develop HD, children may or may not develop HD • 29-35 repeats the individual will not develop HD, children may • <29 repeats, the individual will not develop HD, children will not develop HD

  32. Summary

  33. Summary

  34. Treatment • There is no cure for MD • Medications that are prescribed for MD patients • Steroids • Braces for support • Mobility chairs • Surgery is also an option to release contractures STEM CELL THERAPY !!!!?