Israel Medical Association Journal

Inflammatory myopathies include polymyositis, necrotizing autoimmune myositis, dermatomyositis, juvenile inflammatory myopathy, and inclusion body myositis. These diseases are classified based on the different clinical and pathological characteristics unique to each of them [1]. Dermatomyositis is a rare disease with an incidence of 6–10 cases/1,000,000 a year with the highest incidence in the 7th decade of life as reported by a Norwegian cohort in a Caucasian population [2].

Diagnosis of dermatomyositis is based on typical signs and symptoms combined with laboratory results, imaging, and electromyography findings and muscle biopsy. Historically, the diagnosis of dermatomyositis was based on the classification criteria named after Bohan and Peter published in 1975. Many other classification criteria were proposed subsequently, the latter by the European League Against Rheumatism/American College of Rheumatology (EULAR/ACR), which were published in 2020 [3].

The clinical features of dermatomyositis are diverse. Skin manifestations can accompany or precede muscle weakness. Classical skin findings include periorbital heliotrope rash and a rash of the upper chest, back, and shoulders, known as the V sign and shawl sign respectively, as well as the Gottron's papules on the knuckles. Another skin appearance is subcutaneous calcifications that break periodically through the skin causing ulcerations. Dermatomyositis usually manifests as a symmetrical proximal muscle weakness but can present with preserved strength called amyopathic dermatomyositis [1].

Idiopathic inflammatory myopathies (IIM) are a group of rare, autoimmune, systemic diseases with a large spectrum of clinical phenotypes. The diagnosis and management of myositis demand an integrated evaluation of different clinical, laboratory, and pathological findings in various organs. Recent developments in IIM research, especially in the serological testing and pathology fields, has led to a new classification and better recognition of patients with early or extra-muscular disease, with improvement in clinical care and prognosis.

Background: Polymyositis (PM) and dermatomyositis (DM) are inflammatory mediated myopathies characterized by progressive symmetric proximal muscle weakness and associated with extra-muscular involvement. Central nervous system complications are rarely reported with these diseases.

Objectives: To investigate the association between dementia and PM/DM.

Methods: A retrospective cohort study was conducted using a database from Clalit Health Care, the largest health maintenance organization in Israel. Patients with a first recorded diagnosis of PM/DM were included and were compared with age- and sex-matched controls by a ratio of 1:5. The prevalence of dementia among PM/DM patients compared to controls was assessed using a univariate and a multivariable model. Binary logistic regression analysis was conducted to assess the association of different factors with dementia within the PM/DM cohort.

Results: The study included 2085 PM/DM cases (17.0%) and 10,193 age- and sex-matched controls (83.0%). During the follow-up time, 36 PM/DM patients were diagnosed with dementia compared to 160 controls, with a univariate hazard ratio (HR) of 1.10 (95% confidence interval [95%CI] 0.77–1.58). Within the PM/DM cohort, significant predictors for the development of dementia included increased age at diagnosis (5 years increment; OR 1.86, 95%CI 1.57–2.21, P < 0.001) and treatment with glucocorticoids (OR 5.40, 95%CI 1.67–17.67, P = 0.005).

Conclusions: In our cohort, inflammatory myopathies were not associated with dementia. Age and treatment with glucocorticoids were associated with dementia. If dementia is diagnosed in patients with inflammatory myopathies, other systemic causes should be investigated.

Background: The reported mortality rates of patients with polymyositis and dermatomyositis are highly variable worldwide. The excess mortality of patients with polymyositis/dermatomyositis has not been evaluated in an Israeli population.

Objectives: To investigate the overall mortality in a large and well-established cohort of patients with polymyositis/dermatomyositis as compared to the mortality expected in the matched general population in a tertiary medical center.

Methods: In this retrospective cohort study, the mortality of 166 patients with polymyositis/dermatomyositis was compared to age- and sex-matched control subjects in the general population. All-cause standardized mortality ratios (SMRs) were estimated.

Results: Overall, 47 (28.3%) deaths were observed among patients with polymyositis/dermatomyositis during a mean follow-up period of 5.8 ± 4.8 years, which was 7 times higher than in the control group (SMR 7.4, 95% confidence interval [95%CI] 5.5–9.8). The SMRs were comparable in patents with polymyositis (7.7, 95%CI 4.8–12.3) and dermatomyositis (7.2, 95%CI 5.0–10.3). The 1-, 5-, 10-, and 15-year overall survival rates were 90.0%, 82.8%, 51.5%, and 26.1%, respectively, in patients with polymyositis, and 80.3%, 59.6%, 40.0%, and 17.1%, respectively, in patients with dermatomyositis.

Conclusions: The overall mortality among Israeli patients with polymyositis/dermatomyositis is 7.4 times greater than for the general population. Although long-term mortality was comparable between patients with dermatomyositis and polymyositis, patients in the former group died at a notably earlier stage.