This document discusses idiopathic inflammatory myopathies (IIM), which are rare diseases characterized by symmetrical proximal muscle weakness, elevated skeletal muscle enzymes, and characteristic electromyography and muscle biopsy findings. IIM includes dermatomyositis (DM), polymyositis (PM), necrotizing autoimmune myopathy (NAM), and inclusion body myositis. It most commonly affects women aged 50-59 and can cause difficulty with activities like lifting arms or climbing stairs due to proximal muscle weakness. Investigations may show elevated muscle enzymes or skin rash in DM cases, while management involves immunosuppressive drugs.

2.  Definition
 Epidemiology
 Etiology
 Pathogenesis
 Clinical features
 Investigations
 Management

3.  Idiopathic inflamatory myopathy
 Symmetrical proximal muscle weakness
 Elevated skeletal muscle enzyme
 Characteristic electromyograhic pattern
 Muscle biopsy findings

4.  Rare
 Annual incidence :0.4–1.0 cases per
100,000
 Female preponderance
 Increased with advancing age and reached a
peak at age 50–59 years
 sIBM :the most frequent acquired myopathy
after 50 years of age

6.  Dermatomyositis (DM)
 Polymyositis (PM)
 Necrotizing autoimmune myopathy (NAM)
 Inclusion body myositis

7. Proximal muscle weakness of both upper and
lower limbs causes difficulty in:
 raising arms
 lifting objects
 combing hairs
 difficulty in climbing and descending stairs
 raising from sitting posture

8. GIT
 Dysphagia(30%)
 Bloating
 Constipation

9.  Arrythmias
 Conduction defects
 Myocarditis

10.  Aspiration pneumonia
 Interstitial lung disease(Anti jo-1)
 Bronchiolitis obliterans

11.  Arthralgia
 Calcinosis cutis

13.  Polymyositis
 Characteristic cutaneous findings
 Acute or insidious

21.  CBC: Leukocytosis(50%)
 ESR
 Elevated muscle enzyme
level(CK,LDH,AST,ALT,ALDOLASE)

29. Cutaneous manifestations without
the muscle involvement

30.  Children younger than 18 years of age
 Associated with calcinosis cutis

32.  Cushing Syndrome
 Fibromyalgia
 Hyperthyroidism
 Hypothyroidism
 Polymyalgia Rheumatic
 Rheumatoid Arthritis
 Sarcoidosis
 SLE

33. 1. Symmetrical weakness of limb girdle
muscles
2. Elevated levels of muscle enzymes
3. Myopathy on EMG
4. Muscle biopsy evidence of inflammation
5. Skin rash in the case of DM