polymyositis

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

                                                                                             Image source: googleimage