Organizing pneumonia/non-specific interstitial pneumonia overlap is associated with unfavorable lung disease...

Overlapping forms of interstitial pneumonia have been recognized, but are likely underappreciated, and their clinical, radiologic, and histologic characteristics are not well-defined.

We identified 38 patients with surgical lung biopsy demonstrating histologic organizing pneumonia (OP) or histologic organizing pneumonia/non-specific interstitial pneumonia overlap (OP/NSIP) who met established multi-disciplinary clinical-radiologic-histologic criteria for OP. For each patient, radiologic and co-histologic findings were assessed, and clinical outcome was characterized as disease resolution (complete or near-complete resolution of radiologic opacities and absence of chronic respiratory symptoms) or unfavorable disease progression (death due to respiratory failure or forced vital capacity < 70% predicted > six months from diagnosis).

Seven of 38 patients had clinical-radiologic-histologic focal OP. Focal OP was associated with histologic OP (p = 0.019), and all seven patients demonstrated disease resolution. In the remaining 31 patients with cryptogenic or autoimmune-associated OP, 21 patients had histologic OP/NSIP, and 10 had histologic OP. Histologic OP/NSIP was associated with ground glass opacity (GGO, p = 0.012), reticulation (p = 0.029), traction bronchiectasis (p = 0.029), reactive pneumocytes (p = 0.013), and unfavorable disease progression (p < 0.0001). Histologic OP was associated with consolidation (p = 0.028) and disease resolution (p < 0.0001). Multivariate analysis demonstrated histologic OP/NSIP (p < 0.001) and radiologic GGO (p = 0.041) to be independently associated with unfavorable disease progression.

OP/NSIP overlap, either idiopathic or autoimmune-associated and identified by histologic and radiologic findings, was associated with unfavorable disease progression, and should therefore be recognized as a characteristic clinical-radiologic-histologic entity.