Interstitial pneumonia with autoimmune features

Interstitial pneumonia with autoimmune features (IPAF) is a term given for patients with interstitial lung disease (ILD) who show some features related to autoimmunity but without meeting full criteria for a defined connective tissue disease.

The term is based on the 2015 European Respiratory Society / American Thoracic Society research statement, with the aim of homogenising a specific group of patients, allowing for prospective studies ⁴.

IPAF is defined by the presence of:

• ILD on high-resolution CT and / or surgical lung biopsy, associated with at least one criteria from two of three different domains:
  • clinical
  • laboratorial
  • morphological

Secondary causes of interstitial lung disease, such as external exposure (i.e. silica; asbestos) or collagen disease must be excluded. 

IPAF is an important definition, since only about 15% of this group of patients turn to a collagen disease on a four year follow up ⁵. On the other hand, the prognosis is better than idiopathic interstitial lung diseases, such as IPF ⁶.