Dermatomyositis: An Update on Diagnosis and Treatment

Gabriela A. Cobos; Alisa Femia; Ruth Ann Vleugels


Am J Clin Dermatol. 2020;21(3):339-353. 

In This Article

Abstract and Introduction


Dermatomyositis is a rare inflammatory disease with characteristic cutaneous findings and varying amounts of systemic involvement. Patients may present with skin disease alone, have concomitant muscle disease, or have extracutaneous manifestations such as pulmonary disease or an associated malignancy. Given such diverse presentations, dermatomyositis is both a diagnostic and therapeutic challenge. However, a prompt diagnosis is of utmost importance to institute adequate therapy and screen patients for an associated malignancy. Dermatologists should play a crucial role in the diagnosis and management of patients with dermatomyositis as cutaneous disease tends to be chronic, negatively impact quality of life, and be more recalcitrant to therapy. In this review, we discuss diagnosis, with a focus on myositis-specific antibodies and their associated phenotypes. We also review therapies available for this often refractory skin disease.


Dermatomyositis (DM) is an idiopathic multi-system inflammatory condition. Adult DM, which affects women more than men, remains a rare disease with an annual incidence of 1 per 100,000 persons, though incidence may be increasing.[1–4] While the exact pathogenesis of DM is still not fully elucidated, studies have shown abnormal and upregulated signaling through the interferon pathway.[5,6]

Classic DM (CDM) presents with pathognomonic cutaneous findings and progressive, symmetric proximal muscle weakness. Cutaneous disease precedes the appearance of myositis by 3–6 months in 30–50% of patients, while 10% of patients present with muscle symptoms prior to the development of skin findings.[7,8] There is a subset of patients with DM (approximately 20%) who have a skin-predominant phenotype and are classified as clinically amyopathic DM (CADM).[1,4,9,10] Of note, the diagnosis of CADM is provisional at 6 months and confirmed at 2 years,[10] and encompasses both amyopathic DM and hypomyopathic DM. In a large review of 291 patients with CADM, 70% had amyopathic DM and 13% had hypomyopathic DM.[11] Although both of these subtypes have no clinical evidence of muscle involvement, there is subclinical evidence of muscle involvement demonstrated on laboratory, electrophysiologic, or radiologic evaluations in the hypomyopathic variant.[1,9,12] Both patients with CDM and patients with CADM have an elevated risk of developing interstitial lung disease and occult malignancy.[11,13,14] Post-myopathic DM refers to a subset of patients who have resolution of their muscle involvement with therapy, but have persistent cutaneous disease.[8,11]

Dermatologists should play an integral role in the diagnosis and management of patients with DM as cutaneous involvement is evident in all DM subtypes, often persists after successful treatment of muscle disease, and can greatly impact quality of life.[8,15] The course of cutaneous disease tends to be chronic and prolonged. A prospective cohort of 74 patients with DM receiving various systemic regimens found that only 38% had achieved remission of skin disease in a 3-year follow-up period.[16] With regard to CADM specifically, the role of dermatologists is crucial as many providers have difficulty recognizing DM in the absence of muscle involvement, which often leads to misdiagnosis and contributes to delays in treatment and an appropriate initial workup.[11,13,17] Da Silva et al. found the median delay to correct diagnosis was 17.1 months in patients with CADM, which was significantly higher than patients with CDM (12.2 months).[17] This delay is clinically relevant, particularly with regard to adequately screening patients for malignancy given that the risk is highest in the first 2 years after symptom onset.[14,18,19]