This topic was recently reviewed in Chest. Points of interest:
Estimates are that 35-40% of patients with idiopathic inflammatory myopathy (IIM) will be affected by interstitial lung disease (ILD, named as such for convenience, though perhaps better characterized as diffuse parenchymal lung disease) at some point in their course.
Antisynthetase syndrome is a particular entity characterized by positivity for an antisynthetase antibody (ASA) plus one or more of ILD, myositis, or any of several other rheumatologic manifestations mentioned in the article.
Patients with MA-ILD are generally but not always ASA positive. That is, MA-ILD overlaps considerably with, but does not equal, antisynthetase syndrome.
The principal ASA is Jo-1. There's a miscellaneous group of others seen in lower frequency, listed in the article.
Raynaud's and mechanic's hands are the principal derm manifestations of antisynthetase syndrome.
Derm, pulmonary and muscle manifestations of MA-ILD can occur in any combination, simultaneously or sequentially, and in any order.
Not all pulmonary manifestations of myositis are due to ILD. Muscle weakness itself may contribute to pulmonary complications.
A variety of histologic patterns are seen in MA-ILD the most common of which is NSIP. The prognostic value of histologic types is uncertain.