polymyositis (inflammation of many muscles) is slowly progressing symmetrical weakness of proximal muscle of limbs.
Epidemiology:
- can occurs at any age 30s, 40s, 50s
- women and black are more affected
Cause:
The cause of polymyositis is unknown but genetic, viral infection(retro virus, ) and autoimmune factor play key role in disease initiation.
Pathogenesis:
Humoral attack against the muscle capillaries and arterioles of endomycium which cause inflammation and infiltration.
Clinical feature:
- myalgia
- weakness of muscles i.e shoulder girdle, pelvic girdle cause difficult to raise from seated position, difficult to climb stairs, early fatigue while walking.
- Constitutional symptoms like fever, fatigue, weight loss, anorexia.
- Rheumatic - arthritis/ arthralgia occurs in 20-70% cases
- GI tract - dysmotility of esophagus(dysphasia) occurs in 10-30% cases, constipation
- Cardiac - arrhythmia , conduction block
- Skin- livedo raticularis(net like appearance of skin)
- Pulmonary - dyspnoea, it cause interstitial lung disease, Restrictive ventilatory defect, bronchobstructive syndrome, pneumonia
- vessels - Raynaud’s phenomenon (vasospastic disorder causing discoloration of fingers, toes specially when exposed with cold, change in color from white - blue- red)
Note: no facial rash and no ocular muscle involvement
Malignancy associated with polymyositis are lung cancer, bladder cancer, cancer of nasopharynx, lymphoma (non Hodgkins)
Diagnosis:
- CBC (high ESR, high C reactive protein)
- Serology(anti-Jo 1 antibody)
- History
- physical examination(proximal muscle weakness)
- positive muscle biopsy
- abnormal electromyogram(short duration, short amplitude)
- elevated blood creatinine phosphokinase, aldolase
Treatment:
- Analgesic - Buprenorphine
- Immunosuppressant- prednisolone, cyclosporin
- Antibiotics - clindamycin, amoxycillin/clavulanic Acid
- specialized exercise
- specialized diet
Complication:
- weight loss due to malnutrition(dusphasia), malabsorption
- Aspiration pneumonia
- calcium deposits in skin, muscle, connective tissue (calcinosis)
Prognosis of polymyositis:
- 5 year survival rates have been estimated >80%
- Higher mortality associated with malignancy and cardio-pulmonary complications.
- It respond well with treatment
- 5% of DM patient have a fulminant progressive course
