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Polymyositis and Dermatomyositis

Title               

Ñ    Polymyositis and Dermatomyositis

Definition

Polymyositis

Ñ    Uncommon disorder of unknown cause

Characterised by:

Ñ    Inflammation of striated muscle

Dermatomyositis

Ñ    Skin involvement with polymyositis

Pathogenesis

Causes

Association with malignancy

Ñ    Stomach, lung, ovary, breast (SLOB)

Pathological Process

Ñ    Immune mediated

Ñ    Necrosis of muscle fibres

Ñ    Inflammatory infiltrate with lymphocytes around blood vessels and between muscle fibres

Clinical Features

History

Sex

Ñ    Females  > Males

Age

Ñ    Peak incidence:

Middle age

Onset

Ñ    Usually insidious rarely acute

E&M

Ñ    Malaise

Ñ    Weight loss

Ñ    Fever

CVS

Ñ    Raynaud’s phenomenon

GIT

Ñ    Dysphagia

CNS

Ñ    Dysphonia

LMS

Ñ    Pain

Ñ    Weakness

Examination

E&M

Ñ    Fever

IS

Ñ    Purple discolouration of eyelids, periorbital oedema

Ñ    Widespread erythema with desquamation

Ñ    Gottron’s papules:

Flat topped violaceous papules over the interphalangeal joints

Ñ    Ulcerative vasculitis

Ñ    Subcutaneous calcinosis

RS

Ñ    Respiratory weakness due to paralysis:

Rare

Acute cases

Ñ    Fibrosing alveolitis

Ñ    Aspiration pneumonia

CNS

Ñ    External ocular weakness:

Rare

Ñ    Facial weakness:

Rare

LMS

Ñ    Weakness of proximal limb girdle muscles

Ñ    Pain and tenderness

Ñ    Muscle fibrosis and contractures in the long term

Investigations

Fluids

Blood

Haematology

Ñ    E.S.R.:

Elevated

Biochemistry

Ñ    Creatinine phosphokinase (CPK):

Elevated

Immunology

Ñ    ANA:

·          Positive:

Commonly

Ñ    Rheumatoid Factor:

·          Positive:

50%

Ñ    Anti Jo-1:

Predictive of pulmonary fibrosis

Imaging

MRI

Ñ    Localise and document extent of muscle involvement

Electrophysiology

Electromyography

Ñ    Spontaneous fibrillation potentials at rest

Ñ    Polyphasic or short duration potentials on voluntary contraction

Ñ    Salvoes of repetitive potentials on mechanical stimulation

Tissue Diagnosis

Muscle biopsy

Ñ    Fibre necrosis and regeneration

Ñ    Inflammatory infiltrate with lymphocytes around blood vessels and between muscle fibres

Screen for Malignancy

Ñ    Chest x-ray

Ñ    Mammography

Ñ    Abdominal/pelvic ultrasound

Ñ    Tumour markers

Management

Control

Drugs

Ñ    Steroids

Ñ    Immunosuppression:

Methotrexate, azathioprine, ciclosporin, cyclophosphamide, mycophenolate mofetil

Biological agents

Ñ    Intravenous immunoglobulin

Support

Staffing

Ñ    Physiotherapy

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