Myositis is a rare inflammatory disease that results in damage to muscle fibres and skin, and can also affect other parts of the body. The term myositis describes several diseases including polymyositis, dermatomyositis and myositis by inclusion body.

Myositis often consists of a cycle of exacerbation episodes (active disease) and remissions (periods of inactive illness).

What are the symptoms?

Common symptoms of myositis:

  • Muscle weakness, especially in the hips and shoulders
  • Difficulty swallowing or speaking, a consequence of weakening of the anterior neck and throat muscles
  • Fatigue
  • Fever
  • Lack of appetite
  • Weight loss
  • Difficulty breathing
  • Muscle or joint pain

Other symptoms:

  • Raynaud’s Phenomenon
  • Heart problems such as irregular rhythm or increase in heart size

Polymyositis (PM):

  • Affects more women than men
  • Muscle weakness is commonly proximal (close to the trunk of the body), as well as in the neck and extremities
  • Difficulty passing saliva

Dermatomyositis (DM):

  • Affects more women than men
  • In adults, it can be associated with malignant tumours
  • Can present in children (as a juvenile variant)
  • Muscle weakness is often found in hips, trunk, neck and shoulders

A prominent manifestation is skin rashes. They are usually found around the eyes and on the knuckles, but can occur in other areas:

  • Heliotrope erythema – localized on upper eyelids and around the eyes
  • or Gottron’s papules (violaceous papules or erythematous plaques that appear on bony prominences, such as knuckles, elbows, or knees)
  • or Shawl Signs (V-shaped erythemas distributed as if he were wearing a shawl, on shoulders, nape, high back, chest, and arms,)

Inclusion body myositis (MPI):

  • MPI is more common in men and in those over fifty years, but it can happen in women and at different ages
  • Falling may be the first symptom perceived in some people
  • weakness usually manifests in wrists and fingers
  • Atrophy in forearms and leg muscles

How is it diagnosed?

  • Physical exam
  • Blood tests
  • or CK (creatine kinase)
  • EMG (electromyogram)
  • ECG (electrocardiogram)
  • MRI of affected muscles
  • Muscle biopsy

Treatment options



  • or Corticosteroids (or glucocorticoids)
  • or Methotrexate
  • or Azathioprine
  • or Cyclophosphamide
  • or Chlorambucil
  • or Hydroxychloroquine
  • or IV Ig (intravenous immunoglobulin therapy)
  • Rest

Who is at risk?

Although myositis can affect people of any age, most children who contract the disease are between 5 and 15 years old, while adults are between 30 and 60 years old.

In general, myositis affects more men than women. With the exception of inclusion body myositis (MPI), which affects more men and almost always manifests in older people.