Dermatomyositis Misdiagnosis Common, Affects Outcomes

TOPLINE:

A study found that both dermatomyositis (DM) and clinically amyopathic dermatomyositis (CADM) were commonly misdiagnosed as inflammatory skin disease (ISD), particularly CADM, which was also associated with longer diagnostic delays.

METHODOLOGY:

• Researchers conducted a single-center retrospective cohort study of 260 adults (mean age at diagnosis, 48.6 years; 79% women) with a confirmed diagnosis of DM or CADM and one or more dermatologic visits between 2005 and 2023 at the Johns Hopkins Myositis Center, Baltimore. Most patients were White (69%), Black (19%), and Asian (9%).
• Of these patients, 86 (33%) had CADM and 174 (67%) had DM.
• Study outcomes were ISD diagnoses, hospitalizations, pulmonary function test results, and cancer staging.

TAKEAWAY:

• Overall, 125 patients had an ISD diagnosis; 73 (58%) of these patients were diagnosed with an ISD before being diagnosed with DM or CADM, and 36 (29%) had been misdiagnosed.
• Misdiagnoses were more common in the CADM group than in the DM group (44% vs 21%; P = .006). Median diagnostic delay was longer in the CADM group (236 vs 114 days), but the difference was not statistically significant (P = .34).
• The most common ISDs were unspecified dermatitis (22%) and eczema (19%). Cutaneous lupus erythematosus (67%) and eczema (29%) were the most common misdiagnoses.
• Patients who were misdiagnosed had higher 1-year hospitalization rates (54% vs 33%; P = .02), worse lung function (P = .01), and a higher 1-year incidence of interstitial lung disease (71% vs 43%, P = .03). The prevalence of interstitial lung disease and cancer outcomes was comparable between the two groups.

IN PRACTICE:

DM or CADM “was misdiagnosed as other ISDs, particularly CADM,” the authors wrote, noting that “eczema emerged as a notable mimic, possibly due to similar distributions and morphologic features.” The study findings, they added, suggest that “careful clinical evaluation of atypical cutaneous features is associated with improved disease outcomes.”

SOURCE:

The study was led by Aaron Bao, BA, Department of Dermatology, Johns Hopkins University School of Medicine, Baltimore. It was published online on February 26 in JAMA Dermatology.

LIMITATIONS:

Study limitations included single-center retrospective design and misclassification bias.

DISCLOSURES:

The authors did not disclose any funding source. One author reported receiving personal fees, nonfinancial support, royalties, and holding a patent outside the submitted work. No other disclosures were reported.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.