5th June 2025

Aetiology and Pathophysiology

The aetiology of dermatomyositis is unknown – the current opinion is that it is due to an interaction between environmental factors and genetic susceptibility. 

• Genetic: a genetic predisposition can be inferred from the familial associations investigated
• Immunological: certain HLA subtypes appear to be connected to an increased risk of developing dermatomyositis
• Environmental: overall only weak associations found but the strongest evidence is available for ultraviolet radiation intensity
• Infection: some reports are available of patients with antibodies to Borrelia burgdorferi and Toxoplasma gondii developing myositis; other reports suggest this with viral antibodies, particles, nucleic acids
• Drug-induced: D-penicillamine, hydroxyurea, statins, phenylbutazone, terbinafine

The pathogenesis is unclear, but it is widely accepted to be an autoimmune condition.