WEDNESDAY, Feb. 26, 2025 -- Dermatomyositis (DM) and clinically amyopathic DM (CADM) are often misdiagnosed, according to a research letter published online Feb. 26 in JAMA Dermatology.

Noting that patients with DM often experience misdiagnosis, Aaron Bao, from the Johns Hopkins University School of Medicine in Baltimore, and colleagues identified common dermatologic mimics of DM, compared misdiagnosis rates between DM and CADM subtypes, and characterized potential implications of misdiagnosis. Adults with confirmed DM or CADM diagnosis and one or more Johns Hopkins dermatologic visits between 2005 and 2023 were included in the study.

The analysis included 260 patients: 86 and 174 with CADM and DM, respectively (33 and 67 percent); 125 patients had inflammatory skin disease (ISD). The researchers found that 58 percent of those with ISD received an ISD diagnosis before DM or CADM diagnosis and 36 (29 percent) were misdiagnosed. Seventy-two percent of those with misdiagnosis received their skin evaluation by dermatology. Misdiagnosis rates were higher for the CADM versus DM cohort (44 versus 21 percent), with longer median diagnostic delays (236 versus 114 days). The most prevalent ISDs were unspecified dermatitis and eczema (22 and 19 percent, respectively). The highest misdiagnosis rates were seen for cutaneous lupus erythematosus and eczema before DM or CADM diagnosis (67 and 29 percent, respectively). Higher one-year hospitalization rates were seen for patients with misdiagnosis (54 versus 33 percent).

"Eczema emerged as a notable mimic, possibly due to similar distributions and morphologic features," the authors write.

One author disclosed ties to the biopharmaceutical industry.