26th February 2025

Clinical features of inflammatory myopathies

Symmetrical proximal muscle weakness is the most common finding in both conditions, usually starting in the lower limbs. Muscle pain is less marked than in other conditions such as polymyalgia rheumatica; however, does occur in up to half of cases. 

In addition, dermatomyositis has characteristic cutaneous features. Onset is often weeks to months prior to muscle weakness. Classical cutaneous features include:

• Gottron’s papules: violaceous plaques over the metacarpophalangeal and proximal interphalangeal joints
• Heliotrope rash: a purple-coloured rash around the eyes often associated with periorbital oedema
• Shawl sign: a macular eruption across the back
• V sign: a macular eruption across the anterior chest under the neck

Depending on the antibody, other organ systems may be involved. The most important thing to be aware of is respiratory involvement. ILD is common, and in some autoantibody subtypes can be rapidly progressive. There can also be cardiovascular involvement, and this significantly increases the risk of mortality.