MUSCLE DISEASES
PRIMARY MUSCLE DISEASES:Muscular Dystrophy:
Group of hereditary muscle disease characterized by progressive muscle weakness of skeletal muscle due to defect in muscle protein leading to death of the muscle cell & tissue. Weve 9 types:
Duchenne Muscular Dystrophy:
MOST common, XR, Onset: 1-5 yr, rapidly progressive.
Pelvic then shoulder girdle with GOWER SIGN, then limbs & Respiratory muscles, there is characteristic Pseudohypertrophy of calf muscles, Skeletal Deformity & Muscle Contracture.
Toe walking, Waddling Gait, Frequent Falls, Require wheelchair by 12yr, Death by Third Decade.
CPK 20-100X, EMG: Myopathic changes, MUSCLE Bx: with Histochemistry shows ch Dystrophinopathy.
Mild MR & Cardiac involvement & risk of Gastric Dilatation
Treatment: - oral steroids slows disease progression.
Becker Muscular Dystrohy:
XR, Onset: by 11 yr, death usually by 40s but occasionally normal life span.
Pattern of weakness similar but milder to that of Duchenne M Dystrophy.
Less Crdiac involvement than DMD, Normal Mentality, Less CPK elevation than DMD.
Limb Girdle Muscular Dystrophy (LGMD):
Facioscapulohumeral Dstrophy (FSH):
Emery Driefuss Muscular Dystrophy(EDMD):
Ocular Muscular Dystrophy (OMD): &
Oculopharyngeal Muscular Dystrophy (OPMD):
Distal Muscular Dystrophy:
Paraspinal Muacular Dystrophy:
Myotonia Dystrophica:
AD, onset usually 20-40s, variable severity & progression.
Face: boldness & ch Hatchet Face,
Weakness of Facial, Sternomastoids & Distal limb muscles & ch Myotonia.
Eye: cataract, ptosis & meiosis. Endocrine: DM, Gonadal atrophy, Gynaecomastia, subfertility, Cardiac involvement, Intellectual Decline, Hypersomnia.
Treatment: Phenytoin, Procaineamide or Quinine can help Myotonia.
Otherwise, genetic counselling & Symptomatic Treatment.
Congenital Myopathies:
Heterogeneous group, Rare, Relatively Non Progressive that usually begins in infancy or childhood but may not become clinically evident till adulthood.
Predominantly Proximal muscle weakness, Hypotonia, Hyporeflexia, normal CPK level & diagnosed by Muscle Bx.
Classified according to ultrastructural histopathological features into:
Nemaline Myopathy.
Central Core Myopathy.
Myotubular Myopathy.
Mitochondrial Myopathies:
Heterogenous group of disorders characterised by Defective oxidative phosphorylation & structural mitochondrial abnormalities on skeletal muscle biopsy, the morphological signature is Ragged Red Fibres, usually associated with other systemic manifestations & Variable geneic mode of inheritance.
Inherited Metabolic Myopathy:
Carbohydrate Metabolism Myopathies.Lipid Metabolism Myopathies.
These group of myopathies present with exercise induced Muscle pain, Myoglobinuria.
Inflammatory Myopathies:
Acquired, Subacute or Chr. Inflammatory, Autoimmune Muscle diseases include:Polymyositis (PM): F=M
Occurence at any age with variable progression.
Especially proximal limb & girdle muscles are Painful, Tender in about 65% of pt, leading to weakness & wasting.
Often associated with Dysphagia, Respiratory Difficulty, Raynaud Phenomena, Arthralgia, Fever, and Weight Loss.
Association with Various autoimmune disorders: SLE, Scleroderma, Rheumatoid Arthritis, Sjogren Syndrome.
Malignancy assoc.
Dermatomyositis (DM): F>M
In adition to above there is (skin changes) which precede the syndrome: erethymatous scaly rash on the eye lids (Heliotropic Rash) or on the extensor surface of the joints, there may be photosensitive V shaped rash on the chest or Shawl Sign in shoulders, Gottron Papules as red, raised papules on the extensor surface of elbows, knuckles & interphalangeal joints, mechanics hand & Calcinosis cutis is said to be childhood specific phenomenon.
Inclusion Body Myositis (IBM): M>F
Insidious onset usually after age of 50yr, painless, Refractory.
Early weakness of knee extension with loss of knee jerk then spread to upper limb finger flexors. (Proximal LL & Distal UL) ( Myopathy & Neuropathy)
Etiology unknown: genetic, autoimmune, diabetes, peripheral neuropathy...?
Investigations:
Muscle Enzymes (CPK, LDH, ALT, AST & Aldolase): Hi but normal in IBM.
EMG: Myopathic (CMAP polyphasia low amplitude & short duration) with inflammatory (Insertion Activity: fibrillation & sharp waves), in addition IBM show Neuropathic features.
Muscle Bx: PM ( Perifasciclar inflammatory & CD8 mediated necrosis)
DM ( Endomysial Inflammatory, microangiopathic with complement mediated necrosis)
IBM ( Myopathic & Neuropathic )
Search for associated disease mentioned above: ANA, antiRo/La Ab, anti-Jo Ab ........
Search for Malignancy in adults with PM. DM, IBM
GENETICS
Treatment:
Antiinflammatory Drugs:
Prednisolone tab. with potassium for 2-3 yr. If Fail :
Methotrexate or Azathioprime or Mycophenolate Mofetil.
Immunoglobulin IV Ig.
Physical Therapy.
SECONDARY MUSCLE DISEASES:
Metabolic & Endocrine Myopathy:Osteomalacia.
Hypokalemia.
Hypercalcemia.
Thyroid Myopathy. (hyper & hypo)
Adrenal ( Cushing Syndrome, Addison disease & Conns Syndrome)
Drug Induced Myopathy:
Corticosteroids.Statins.
B- Blockers.
Alcohol.
VIII- Infective Myopathy:
Virus Myositis
Toxoplasmosis.
Trichenosis..
Toxin Myopathy:
Alcohol.Organophosphorus.
Vitamin E.
Snake Venom.
Lec 1 Dr Heewa A. Younis
1ST NOV 2015
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