ORLANDO – 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, and remain vigilant for erythema on the lateral thighs or nasolabial fold, Gottron’s papules, and other diagnostic giveaways, the researchers said.
Interface dermatitis, in particular, can’t be relied on to differentiate the conditions. Ais 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.