Limited pulmonary MPA, a new MPA entity? A rheumatologist's perspective.

Microscopic polyangiitis (MPA) frequently involves the lungs. However, as opposed to granulomatosis with polyangiitis (Wegener's), limited forms are not recognised. In recent years, cases have been reported in which the lungs were affected without other organ manifestations. For years, many have been labelled as idiopathic pulmonary fibrosis (IPF). In this review, support for the existence of a limited form of MPA affecting the lungs as well as questions and discussions concerning the similarities and differences to IPF are offered.