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Timely dermatomyositis diagnosis, treatment remain elusive

 

Key clinical point: Clinicians need to do a better job of catching DM early.

Major finding: It took a median of 12.2 months after the start of symptoms to diagnose classic dermatomyositis, and 17.1 months to diagnose amyopathic dermatomyositis.

Study details: Review of 232 patients

Disclosures: There was no industry funding, and the presenter didn’t have any disclosures.

Source: da Silva DM et al. Presented at the 2018 International Conference on Cutaneous Lupus Erythematosus
 


 

REPORTING FROM ICCLE 2018

– There was a median 1-year delay between the onset of symptoms and diagnosis of classic dermatomyositis, and a 17-month delay before diagnosis of amyopathic dermatomyositis, based on a review of 232 dermatomyositis patients seen at the University of Pennsylvania, Philadelphia.

Just 103 (44.4%) patients were diagnosed with dermatomyositis (DM) right out of the gate. Among the other 129, 48 (37.2%) were diagnosed with lupus, 38 (29.5%) with undifferentiated connective tissue disease, 10 (7.8%) went undiagnosed, and 33 (25.5%) were diagnosed with rosacea, psoriasis, rheumatoid arthritis, fibromyalgia, lichen planus, and a number of other conditions. By the time the DM diagnosis was finally confirmed, almost every patient had Gottron’s papules or sign.

Misdiagnosis of dermatomyositis (DM) is nothing new, but the study brings home just how common the problem is, even at a major academic medical institution.

One of the take homes is that clinicians should never forget about the possibility of DM even when patients are diagnosed with other autoimmune diseases, and remain vigilant for erythema on the lateral thighs or nasolabial fold, Gottron’s papules, and other diagnostic giveaways, the researchers said.

Basil Patel, MD, University of Pennsylvania, Philadelphia. M. Alexander Otto/MDedge News

Dr. Basil Patel

“Biopsies for lupus and DM can be essentially identical,” with interface dermatitis and dermal mucin found in both. “We see a lot of patients misdiagnosed with” cutaneous or systemic lupus, said investigator Basil Patel, MD, a research fellow at the university.

Interface dermatitis, in particular, can’t be relied on to differentiate the conditions. A better option is checking for lupus bands and membrane attack complexes on direct immunofluorescence.

There’s also just not enough awareness that dermatomyositis can present without the classic muscle symptoms and findings, i.e. clinically amyopathic DM. While 49 of 120 patients with classic dermatomyositis (40.8%) were misdiagnosed or undiagnosed in the study, the number rose to 80 of 112 (71.4%) among amyopathic patients.

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