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

## TL;DR

A 67-year-old man with steroid-resistant cryptogenic organizing pneumonia showed improvement with hydroxychloroquine after being found to have a deficiency in mannose-binding lectin, which may affect cell clearance and inflammation.

## Contribution

This case proposes a novel link between mannose-binding lectin deficiency and steroid-refractory cryptogenic organizing pneumonia, suggesting hydroxychloroquine as a potential treatment.

## Key findings

- The patient had frequent exacerbations of cryptogenic organizing pneumonia despite standard steroid therapy.
- Mannose-binding lectin deficiency was identified, potentially impairing apoptotic cell clearance and contributing to inflammation.
- Low-dose hydroxychloroquine led to disease remission, indicating a possible immunomodulatory treatment approach.

## Abstract

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.

A 67‐year‐old man with cryptogenic organising pneumonia developed recurrent relapses despite corticosteroid and mycophenolate therapy. A complete absence of mannose‐binding lectin was identified, suggesting impaired apoptotic cell clearance as a contributor to persistent inflammation. Disease remission was finally achieved with low‐dose hydroxychloroquine, highlighting a potential immunomodulatory approach in steroid‐refractory cases.