Polymyositis & Dermatmyositis
These are connective tissue disorders with inflammatory reaction in skeletal muscles and / OR skin of autoimmune pathogenesis .
Lymphocystic Infiltration of skeletal muscles .
1- Primary idiopathic polymyositis .
2- Primary idiopathic dermatomyositis (polymyositis + skin lesion).
3- Dermatomyositis or polymyositis associated with malignancy.
4- Childhood dermatomyositis.
5- Polymyositis or dermatomyositis associated with other connective tissue disorders e.g. (mixed connective tissue disease).
How to diagnose Polymyositis & Dermatmyositis ?Clinical picture :
It is an inflammatory myopathy, occurs at age of 30-60 years, female to male ratio 3 : 1 with insidious onset.
1- Muscle :
- There is bilateral proximal weakness (shoulder and pelvic girdle muscles). The muscles may be wasted but are not usually tender.
- Face and distal limb muscles are not usually affected.
- Tendon jerks are preserved.
Heliotope rash : It is a violaceous discoloration of the upper eyelids, forehead and nasolabial folds.
Gottron's sign : erythematous eruption over the extensor surfaces of P.I.P joints and M.P joints.
3. Joint : Arthralgia.
4. Heart : Myocarditis causing heart failure, arrythrmias.
5- Malignancy : this occurs particularly in males with dermatomyositis with age of 50 years or more so, you must to search for malignancy:
• Lung • Prostate, ovary • Colon • Cancer breast
6- Raynaud's phenomenon
7- Lung : Interstitial pulmonary disease.
8- GIT : Dysphagia due to esophageal dysmotility (myositis of striated muscle in the upper one third of esophagus
Violaceous discoloration similar to heliotrope rash may occur on the upper back, chest and shoulders ( Shawl distribution) .
• Electromyography : showing myopathic changes.
• Muscle biopsy from quadriceps or deltoid --> features of fibre necrosis, regeneration and inflammatory cell infiltrate.
MRI is a useful mean of identifying areas of abnormal muscle that are suitable to biopsy as the myositis may be patchy. The ideal muscle to sample for biopsy is one that is involved but not atrophic .
• Creatine kinase (CK) is usually raised and is a guide to disease activity, however a normal CK does not exclude the diagnosis.
• ANA positive in 50-80 of cases, rheumatoid factor positive in 50% of cases .
• Myositis specific antibody e.g. Anti-Jo-1 (antibody to histidyl tRNA synthetase) 30 %.
• ESR is high during disease activity in about 50%.
Antisynthetase syndrome:About 20-30% of patients with PM.or DrM have antibodies to t RNA synthetase enzymes, these patients are more liable to interstitial
pulmonary fibrosis, arthritis, Haynauld's phenomenon and fissuring of skin over the pulp of the finqers (mechanic's hand).
What is the treatment and management of Polymyositis & Dermatmyositis ?1- Search for neoplasm any where.
2- Steroids : 60 mg / day Prednisolone till improvement i.e, S and S and CK become Low
Then maintenance 10-15 mg / day .
3- Immunosuppressive drugs can be used with small dose steroid e.g. azathioprine. or methotrexate. If these drugs are ineffective we can use
cyclosporin, cyclophosphamide or tacrolimus .
Pulse steroid therapy may be used in cases with severe weakness or with respiratory or pharyngeal weakness .