Detailed physical exam, medical history key to 'ruling out' dermatomyositis from lupus
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A thorough physical exam and attention to a patient’s medical history are integral to differentiating dermatomyositis from cutaneous dermatomyositis with similar features, according to a presenter here.
“Our two specialties have a lot of overlap,” Alisa N. Femia, MD, a dermatologist at NYU Langone Health, said in her presentation, most notably between various types of cutaneous dermatomyositis and cutaneous lupus.
As a starting point, Femia encouraged clinicians “dive into” the medical histories of their patients. She also suggested that patients should be encouraged to document history of skin changes.
Another pointer is to dress the patient in a gown and do a thorough exam that includes personal or hard-to-reach areas that patients may be shy about discussing.
To that point, cutaneous dermatomyositis often happens on the upper thighs, according to Femia. In addition, a heliotrope rash on the face is usually cutaneous dermatomyositis and not generally cutaneous lupus.
Gottron papules, frequently found on the hands, also are likely to indicate dermatomyositis rather than lupus. “Lupus really does not like extensor surfaces, whereas dermatomyositis likes extensor surfaces,” Femia said.
Similarly, nailfold capillary changes may also clue a rheumatologist into a diagnosis of cutaneous dermatomyositis. In addition, clinically amyopathic dermatomyositis carries the same risk for malignancy and lung involvement as its myopathic counterpart, according to Femia.
Keeping an open mind is also critical in appropriately diagnosing dermatomyositis. Eczema may resemble spongiotic dermatitis or even a nickel allergy. “If you think you are seeing something on your patient’s skin, follow it to ruling out a diagnosis, or leading to a diagnosis, even if there are other factors that are leading you astray,” Femia said.
Melanoma differentiation-associated protein 5 (MDA5)-positive dermatomyositis can present diagnostic challenges, largely because it is typically amyopathic, according to Femia. “It is often associated with interstitial lung disease, which is very often fatal,” she said.
Cutaneous ulcers may be present in MDA5-positive disease, along with palmar papules, all of which can be “exquisitely painful,” Femia added. “Treat them with vascular type therapies,” she said, or drugs that can be used in Raynaud’s phenomenon.
Rheumatologists may be challenged by patients with dysphagia, myositis, periorbital edema and calcinosis cutis. “This tends to be one of the most frustrating diagnoses in the dermatology world,” Femia said.
A combination of medical and surgical interventions may be optimal in these cases. However, because the nodules can be so visually unpleasant, many patients desire surgical intervention. “But the nodules just recur if the underlying disease is not managed,” Femia said. That said, sodium bisphosphonate applied topically or injected intralesionally generally yields the best outcomes in terms of reducing nodules and improving physical appearance.
For patients with immune checkpoint inhibitor therapy-induced myositis, those with typical manifestations tended to have a good prognosis, according to Femia. “More atypical disease tended to have a worse prognosis,” she said. Immunosuppressive therapy beyond steroids is recommended for this patient population.
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Femia AN. Dermatology for the Rheumatologist, Part I. Presented at: Congress of Clinical Rheumatology-East annual symposium; August 12-15, 2021 (hybrid meeting).
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