Sometimes patients with polymyositis also have other rheumatologic conditions that shouldn’t be overlooked, therefore “overlap is its own category,” she said.
“In our experience, the most common overlap is scleroderma,” she noted, adding that the scleroderma is often, but not always, subtle, and that there may be overlapping autoantibodies.
Overt sclerodactyly is rarely seen, although a small amount may be present, but significant Raynaud’s phenomenon is common in these patients, and tiny telangiectasias across the neck are a tell-tale sign.
“Why does that matter? It’s not an esoteric argument; those are the folks that go on to have pulmonary hypertension,” she said. “They can have the same [interstitial lung disease] and all of the other internal scleroderma manifestations.”
Think about overlap and “look close phenotypically and with antibodies,” she advised.
There is also “the typical RA seropositive overlap,” she said, but lupus only rarely overlaps with myositis.
“However, the next diagnosis on the list – antisynthetase syndrome – can be a forme fruste where you first see a seronegative RA-like picture, and it’s important to think about that as well,” she said.