Dermatomyositis

Dermatomyositis is an acquired immune-mediated muscle disease characterized by muscle weakness and skin rash.

Clinical features:-

1. Progressive and painless symmetric proximal muscle weakness that leads to difficulty climbing stairs, arising from chairs, combing hair; Usually involves lower limbs more than upper limbs; Involvement of pharyngeal, laryngeal and respiratory muscles can lead to dysphagia, dysphonia and respiratory failure.

2. GI:- dysphagia.

3. CVS:- conduction abnormalities, congestive heart failure, arrhythmias.

4. Pulmonary:- ILD; Antisynthetase syndrome:- acute onset DM with rapidly progressive ILD (MC manifestation), fever, weight loss, Raynaud’s phenomenon, mechanic’s hands, arthritis. It is most commonly a/w Anti Jo-1 (histidyl tRNA synthetase) antibodies.

5. MSK:- non erosive arthritis.

6. Systemic features like fever, weight loss and fatigue are common.

Presents with proximal muscle weakness and typical dermatological manifestations (i.e. Heliotrope rash, gottron’s papule, shawl sign, mechanic hands).

Diagnosis:-

1. Inflammatory markers (i.e. ESR and CRP are increased).

2. Muscle enzymes (e.g. CK, aldolase, LDH) are elevated.

3. Anti Jo-1 (histidyl-tRNA synthetase), Anti Mi-2, Anti SRP antibodies are positive.

4. EMG

5. MRI

6. Muscle biopsy shows perimysial inflammation with CD4+ T cells and atrophy.

Treatment:-

1. High dose steroids.

2. Immunosuppressants (e.g. azathioprine, mycophenolate or methotrexate) are used if patients are not responsive or intolerant of steroids.

3. IVIG.