Primary and secondary vasculitis of the lung - critical evaluation of the update classification.

Vasculitis in the lung can be separated into infectious and non-infectious, and in systemic and localized ones. Three major categories in the lung are known, previously named Wegener's granulomatosis, Churg-Strauss syndrome, and microscopic polyangiitis. The classification of vasculitis was proposed in 1994, including a size distribution for each type, an antinuclear and anticytoplasmic antibody profile (ANCA), and an organ location. In an updated classification (2011) the names for two of the most common primary vasculitis were replaced: Wegener`s granulomatosis by Granulomatosis with polyangiitis (GPA) and Churg-Strauss syndrome by Eosinophilic granulomatosis with polyangiitis (EGPA). This proposal has been critically discussed in meetings of the pulmonary working group of ESP (2025) and the Pulmonary Pathology Society Meeting (Quebec, 2026). There were doubts about the usefulness of the when applied in pulmonary pathology. A new proposal is presented here. This classification is based on pattern recognition, such as neutrophilic, eosinophilic, and other forms of vasculitis. As many other types of pulmonary vasculitis were not covered in the old nor in the new proposal, several variants are added. This applies for example to vasculitis seen in autoimmune diseases. There is no doubt, that a classification of vasculitis is important, to sort the type of vasculitis. If possible, such a classification should be useful not only in lung pathology but more general in any other organ system. However, in several organ systems the clinical picture and the laboratory test allow a diagnosis, which is not the case in lung. On CT scan most types of pulmonary vasculitis present with ground glass opacitis with/without nodules. Often biopsies are labelled as interstitial lung disease.