Dermatomyositis (DM) is a rare autoimmune family of diseases in which the muscles and skin are affected by inflammation. They can occur in childhood or in adults. The autoimmune aspect of these diseases is associated in 60% of patients with the presence of DM-specific antibodies, among which the anti-SAE antibody is rare.
In a retrospective observational study (NCT0463767), a team involving researchers and clinicians from the Institute of Myology described the clinical characteristics, cancer prevalence and muscle pathology of anti-SAE (anti-small ubiquitin-like modifier activating enzyme) positive DMs. Forty-nine patients (84% female) with a diagnosis of DM and sera positive for anti-SAE were recruited from 19 centres. Available muscle biosynthetic therapies were reviewed and compared with anti-SAE negative DMs and a review of the literature.
The results show that :
- skin involvement was typical in 96% of cases
- muscle disease concerned 84% of patients, with mild weakness, although 39% had dysphagia
- muscle biopsies showed typical DM lesions:
- interstitial lung disease was found in 21% of patients, mainly in the form of organised pneumonia;
- 26% of patients had dyspnoea;
- Cancer-associated myositis was diagnosed in 16% of patients and was responsible for the majority of deaths;
- comparison with anti-SAE negative dermatomyositis shows less and milder muscle weakness, lower creatinine kinase levels and less dyspnoea.
The authors conclude that anti-SAE positive DM is a rare subgroup associated with typical skin features, as well as possible diffuse rash, mild myopathy and less severe muscle involvement. The prevalence of cancer in this DM is five times higher than in the general population.
