Diagnosis and Management of Dermatomyositis

Clinical Presentation and Diagnosis

The European League Against Rheumatism (EULAR) recommends that the diagnosis of dermatomyositis be based on a combination of clinical, laboratory, and histopathological findings, including characteristic skin lesions, proximal muscle weakness, elevated creatine phosphokinase (CPK) levels, and positive anti-nuclear antibodies (ANA) 1.
The American College of Rheumatology (ACR) suggests that the presence of Gottron's sign, heliotrope rash, and periungual telangiectasias are highly specific for dermatomyositis, with a sensitivity of 59% and a specificity of 98% 1.
Muscle biopsy is the gold standard for confirming the diagnosis of dermatomyositis and distinguishing it from other types of myopathy, with a sensitivity of 79% and a specificity of 93% 1, 2, 3, 4.

The EULAR/ACR 2017 criteria for the diagnosis of dermatomyositis include a combination of clinical, laboratory, and histopathological findings, with a total score of ≥5.5 required for a definitive diagnosis 1.
The criteria include age ≥40 years (2.1 points), proximal muscle weakness (0.8 points), Gottron's sign (3.3 points), elevated CPK (1.3 points), and positive ANA (1.2 points) 1.

The American Cancer Society recommends that patients with dermatomyositis undergo comprehensive cancer screening, including imaging studies and laboratory tests, due to the increased risk of malignancy, particularly in patients >40 years old 2, 3.
The National Comprehensive Cancer Network (NCCN) suggests that the screening should include a thorough history and physical examination, complete blood count, chemistry profile, and tumor markers (CEA, CA-125, CA 19-9) 2, 3.
The European Respiratory Society recommends that patients with dermatomyositis undergo pulmonary function tests and high-resolution computed tomography (HRCT) of the chest to evaluate for interstitial lung disease, which can be a rapidly progressive and fatal complication 2.