Myopathies

Duchene's Muscular Dystrophy

(*most common childhood Myopathy) X - linked recessive disorder Onset early childhood, patients do not demonstrate weakness until age 3 - 5 years Initial progressive proximal weakness, then distal weakness, respiratory distress and death by 3rd decade Death is usually by *respiratory infection (pneumonia and inability to oxygenate) and/or cardiac malfunction 2' to fatty infiltration of myocardium

Muscular Dystrophy

A group of inherited myopathic disorders characterized by slowly progressive muscle weakness, wasting and proliferation of fatty and connective tissue Subdivided by mode of inheritance, age of onset and clinical features and also mental retardation vs. normal mental development

Malignant hyperthermia

A hereditary condition of uncontrolled heat production that occurs when susceptible people receive certain anesthetic drugs.

myopathy definition

Any abnormal state of striated muscle, presenting with muscle weakness, pain, cramps, muscle tenderness, and spasms of various degree

Key factors of Dx of Myopathies

Symmetric proximal disorders without sensory component (weak shoulders or hips) *Different from peripheral neuropathy typically presents with distal weakness and sensory loss

Bulbar symptoms

-can be a sign of myopathy Upper Motor Neuron Manifestations - Dysphagia - Dysarthria - Diplopia - Emotional lability - Voice change

Side effects of Statins

1. increase plasma transaminases (AST/ALT), 2.Myopathy=increased CK-MM, mm tenderness, pain, weakness, rhabdomyolosis, renal dysfunction, 3. reports of LUPUS-LIKE syndrome, dose related increases in LFTs (check at baseline and every 6-8 wks; myopathy/myositis/rhabdomyolysis

Rhabdomyolysis

A condition in which damaged skeletal muscle tissue breaks down rapidly. Breakdown products of damaged muscle cells are released into the bloodstream; some of these, such as the protein myoglobin, are harmful to the kidneys and may lead to kidney failure -Recent exercise - Trauma - Alcohol binges - Recent chronic ingestion of statins, niacin, clofibrate or gemfibrozil - history of tea colored urine and/or myalgias

Guillain-Barre

A rapidly progressing disease that affects the motor component of the PNS -can initially present with the common cold or after a surgery. , Acute asymmetric ascending inflammatory neuropathy; Weakness begins in lower and ascends; respiratory failure can occur in sever cases; reflexes invariably decreased or absents; 2/3 of patient have respiratory or GI illness 1-3 weeks prior to onset; Albuminocytologic dissociation

Endocrine Myopathies

Adrenal dysfunction - Cushing's syndrome Thyroid dysfunction - Myxedema coma or thyrotoxic Parathyroid dysfunction - endocrine neoplasia **Pituitary dysfunction Islands of Langerhans dysfunction

Myotonic Muscular Dystrophy

Autosomal dominant disorder Onset age 2 - 25 years Distal weakness Cataracts* Frontal balding Impaired intellect Hypersomnia Cardiomyopathy, arrhythmia Most prevalent adult form Death by age 50 - 60 years

CREST Syndrome

C-calcinosis, R-Raynaud's Phenomenon, E-Esophageal Dysfunction, S-Sclerodactyly, T-Telangiectasia (dilation of capillaries) -- A variant of PSS

Polymyalgia Rheumatica

Characterized by pain and stiffness in muscles of the limb girdle Elderly Often in conjunction with **Temporal Arthritis Sx - weight loss, fatigue, fever, pain and stiffness of the shoulders and thighs, worse at HS and in AM RX - symptomatic Classically can present with a long term influenza type illness (A or B)

Etiologies of *acquired myopathies

Childhood- inflammatory, infectious or endocrine Adult- inflammatory, infection, endocrine, toxic. --Steroids -- Statins (rhabdomyolysis) - Sulfonylurea's - Aminoglycoside antibiotics -Alcohol abuse systemic illness - Cancer - Thyroid disease - HIV - Diabetes - Hepatic or Renal failure - Pituitary dysfunction - Connective tissue disease

Inherited forms of Myopathy

Dystrophies characterized by muscle degeneration and regeneration until the muscle can no longer maintain > then weakness and progression *more proximal than distal Congenital - decreased contractile ability at birth (FMH is the key to making a DX) Hereditary causes: --Amyotrophic Lateral Sclerosis (10%) -- Muscular Dystrophy -- Glycogen and Lipid Storage disorders -- Spinal muscle atrophy

Myasthenia Gravis

Insidious onset More common in young women Presentation - ptosis, diplopia,difficulty chewing, swallowing, respiratory fatigue, limb weakness Symptoms fluctuate Sensation normal, reflexes normal *Edrophonium testing to Dx.

How to approach clinical patient with myopathy

Most are a diagnosis on clinical grounds Labs -- Creatinine Kinase with isoenzymes(what muscle is causing the elevated kinase, cardiac, intestinal) --Electrolytes --ESR (is going to establish inflammation in the body) --ANA & RF --EMG (impairment of neuro fucntion) --Muscle biopsy --Imaging studies as indicated

Polymyositis

One of the most common diseases of striated muscle, skin, and surrounding connective tissue **Muscle weakness fluctuates weekly Ocular muscles remain normal, but neck and pharyngeal muscles affected Sensation remains normal

Limb-Girdle Muscular Dystrophy

Onset age 10 - 20 can be delayed as long as middle age Shoulder and pelvic girdle muscles involved Severe disability 20-30 years post onset Can be transmitted as both autosomal dominant and recessive trait, this determines muscle groups involved (fatigue easily if they are driving any distances)

Amyotrophic Lateral Sclerosis

Predominantly male disease Age of onset 55 - 75 years Progressive upper and lower neuron signs in multiple regions 20% demonstrate dysarthria, dysphagia, drooling, emotional lability Most common distribution of initial weakness is asymmetric and focal mortality - respiratory infection or bowel obstructions.

Inclusion Body Myositis

Progressive inflammatory myopathy of unknown cause Age > 50 years Proximal and distal muscle weakness, progressive and painless Wrist and knee flexors occur early

PE of Myopathy

What can patient look like? moon facies, temporal wasting, cataract, drooling, hypophonia, fish mouth - myotonic dystrophy Lungs- effort and rate CV- cardiomyopathies Abdominal - striae, hepatosplenomegaly Back - Cushing Hump -tibial myxedema -Goittron's papules on knuckles periorbital purplish rash Fragile skin Neurological Motor exam: lethargy and CO2 retention due to respiratory fatigue Cranial nerve or tongue bulbar involvement to a motor exam : score muscle strength.

Important aspect of Hx "myopathies"

When did symptoms begin Where did the symptoms begin (using arms to rise out of chair, using elevator instead of stairs, diffculty with use of muscle) Acute or gradual onset (How did it develop and progress) Have the symptoms been constant or intermittent - Fluctuations in weakness think neuromuscular junction disorders or electrolyte - If long standing or early onset - possible hereditary cause Proximal vs. distal (proximal - gross motor movements) (distal - fine motor movement) - Symmetric vs. asymmetric - Focal vs. multifocal - Motor or sensory or both

Dermatomyositis

Women more commonly affected Proximal limbs are weaker than distal and develops over several weeks Dysphagia and difficulty climbing stairs and combing hair Rashes Heliotrope - purplish and periorbital V sign photosensitive chest rash Goittron's papules scaly rash of knuckles **Usually occurs in conjunction with Scleroderma, *CREST Syndrome (incomplete scleroderma) and malignancy

Becker's Muscular Dystrophy

X - linked recessive disorder Typically occurs in males More benign course - most walk into their 20's 50% survival into 5th decade Predominantly proximal symptoms of the pelvic and shoulder girdle (*typically difficulty in using their arms)