Steroid-Refractory Cryptogenic Organising Pneumonia (COP) in a Patient With Mannose-Binding Lectin (MBL) Deficiency.

We report a 67-year-old man with a relapse characterised by fever, respiratory failure and bilateral infiltrates following completion of a short-term empirical methylprednisolone regimen for a similar episode. Serum, upper respiratory tract and bronchoalveolar lavage samples were negative for infection, whereas an extensive antibody panel showed no remarkable findings. The presence of migratory opacities on chest imaging, a mixed cellular lavage pattern and prior steroid responsiveness supported a provisional diagnosis of cryptogenic organising pneumonia. During outpatient follow-up, frequent exacerbations occurred, barring any steroid tapering attempts. An individualised pathophysiological hypothesis is proposed for the recalcitrant course following incidental detection of mannose-binding lectin deficiency. Given the potential role of mannose binding lectin in apoptotic cell clearance and modulation of inflammation, we postulate an impingement on the disease trajectory, which has been previously observed in chronic obstructive pulmonary disease, bronchiectasis and bronchiolitis obliterans post-transplant.