Dermatomyositis and Polymyositis (DM/PM)

Author: Shelley Ensz. Scleroderma is highly variable. See Types of Scleroderma. Read Disclaimer
Myopathy and Myositis
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Myopathy and Myositis

Dermatomyositis KaleidoscopeMyopathy vs. Myositis. Myopathy means muscle disease. Myositis means muscle disease that is caused by inflammation. There are three types of myositis: dermatomyositis, polymyositis, and inclusion body myositis. ISN.

Myopathy vs. Myositis
Myopathies and Scleroderma
Myopathies and Overlapping Diseases

What is Dermatomyositis?

Inflammatory muscle weakness plus skin rashes

Dermatomyositis is an inflammatory skin and muscle disease. Distinctive rashes on the hands, feet, elbows, face, and/or upper body, occurring along with muscle weakness, are hallmark symptoms. (Also see Autoimmune Diseases)

What is Polymyositis?

Inflammatory muscle weakness without skin rashes

Polymyositis is an inflammatory muscle disease. It's hallmark symptom is extreme muscle weakness, usually in the neck, upper arms, and thighs. When polymyositis occurs along with a skin rash, it is called dermatomyositis.

What is Polymyositis? It is a muscle disease featuring inflammation of the muscle fibers, typically those closest to the trunk or torso. This results in weakness that can be severe.

Symptoms of Dermatomyositis and Polymyositis

Dermatomyositis Symptoms
Polymyositis Symptoms

Diagnosis of Dermatomyositis and Polymyositis

Endothelial and inflammatory biomarker profile at diagnosis reflects clinical heterogeneity of juvenile dermatomyositis (JDM) and is prognostic for response to treatment in two independent cohorts. This study confirms the heterogeneity of new-onset JDM using serum biomarkers. PubMed, Arthritis Rheumatol, 02/26/2020.

Case Report: NXP-2 Positive Dermatomyositis: A Unique Clinical Presentation. Nuclear matrix protein (NXP-2) antibodies have been described as a myositis–specific antibody that may aid in the diagnostic evaluation. PubMed, Case Rep Rheumatol.

State of the art on nailfold capillaroscopy (NFC) in dermatomyositis (DM) and polymyositis (PM). The overview confirms that NFC is a safe and noninvasive tool able to help the clinician in the diagnosis of DM and PM and to better characterize the phase of disease activity of these patients. PubMed, Semin Arthritis Rheum, 06/28/2017. (Also see Nailfold Capillaroscopy)

Mortality and Prognosis of DM/PM

Galectin-9 and CXCL10 as biomarkers for disease activity in juvenile dermatomyositis (JDM): a longitudinal cohort study and multi–cohort validation. Galectin-9 and CXCL10 were validated as sensitive and reliable biomarkers for disease activity in (J)DM and implementation of these biomarkers into clinical practice might facilitate personalized treatment strategies. PubMed, Arthritis Rheumatol, 03/12/2019.

Radiological images of interstitial pneumonia in mixed connective tissue disease (MCTD) compared with scleroderma (SSc) and polymyositis/dermatomyositis(PM/DM). HRCT images in MCTD patients can be classified as SSc pattern or PM/DM pattern. PubMed, Eur J Radiol, 2018 Oct;107:26-32. (Also see Correlation between Pulmonary Fibrosis and other Diseases and Mixed Connective Tissue Disease)

Anti-NT5C1A autoantibodies are associated with more severe disease in patients with juvenile myositis. As in adults with inclusion body myositis, patients with juvenile myositis with anti-NT5C1A autoantibodies have more severe disease. PubMed, Ann Rheum Dis, 2018 May;77(5):714-719.

Cardiac Function in Patients With Polymyositis (PM) or Dermatomyositis (DM): A Three-Dimensional Speckle-Tracking Echocardiography Study. Our results suggest that cardiac injury in PM/DM is a long-term process and its severity depends on patients' heterogeneous clinical features and systemic disease burden. PubMed, Int J Cardiovasc Imaging, 2018 May;34(5):683-693. (Also see Complications with Heart Involvement)

Treatments for Dermatomyositis and Polymyositis

Biological Agents
CB2 Agonist
Combination Therapies
Stem Cell Transplants


The RIG-I pathway is involved in peripheral T cell lymphopenia in patients with dermatomyositis (DM). Our study showed for the first time that negative correlation between the increased RIG-I expression in peripheral T lymphocyte and T cell count in some patients with DM. PubMed, Arthritis Res Ther, 2019 May 29;21(1):131.

The relationship between type 1 IFN and vasculopathy in anti-MDA5 antibody–positive dermatomyositis (DM) patients. The high T1-IFN signatures of the MDA5 antibody–positive DM patients in serum and deep vasculatures suggested that T1-IFN may have important roles in the vasculopathy of these patients. PubMed, Rheumatology (Oxford), 12/11/2018.

Muscular and extramuscular clinical features of patients with anti-PM/Scl autoantibodies. Anti-PM/Scl-positive patients have weaker arm abductors than hip flexors and also have the most extensive extramuscular features. PubMed, Neurology. 2018 Jun 5;90(23):e2068-e2076. (Also see Antibodies)

Polymyositis: Can a gluten-free diet reduce symptoms? If you have polymyositis — a rare connective tissue disease — you may be at increased risk of celiac disease. In such cases, a gluten-free diet can improve signs and symptoms of celiac disease. But there's no evidence that a gluten-free diet can improve signs and symptoms of polymyositis. Mayo Clinic. (Also see Celiac Disease and Gluten Sensitivity)

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