Bird fancier's lung ICD-10 J67.2 · ICD-11 CA70.2

Nonfibrotic Bird Fancier's Lung After Steroid-Sparing Immunosuppressants Fail to Stabilize Lung Function

This protocol addresses the management of hypersensitivity pneumonitis in its nonfibrotic (inflammatory) phenotype — specifically when a steroid-sparing immunosuppressive regimen has been tried and lung function has not improved or stabilized.

Clinical scenario

The patient has hypersensitivity pneumonitis without radiological or histopathological pulmonary fibrosis — the nonfibrotic phenotype. Active inflammation is present, evidenced by ground glass opacities (GGO) on HRCT and lymphocytosis on bronchoalveolar lavage (BAL). International diagnostic guidelines distinguish this phenotype from fibrotic HP because its prognostic and treatment implications differ meaningfully.

Previous line — why escalation is needed

A steroid-sparing immunosuppressive agent was added — from among mycophenolate mofetil, azathioprine, cyclophosphamide, or methotrexate — but the primary goals of that step were not reached: lung function (DLCO and FVC) did not show adequate improvement or stabilization. This failure to meet those targets is the criterion that triggers escalation to the current protocol.

Next-step treatment approach partial preview

After failure of second-line steroid-sparing therapy, the approach moves to a third-line immunosuppressive agent. One such agent — rituximab — has case series-level evidence in this setting. The complete selection criteria, sequencing, and clinical guidance are in the full protocol.

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References

  1. Recently published international diagnostic guidelines recommend HP classification into fibrotic or nonfibrotic phenotypes based on the presence or absence of radiological and/or histopathological fibrosis, supported by the observation that pulmonary fibrosis conveys important prognostic and treatment implications.
  2. Moderate-to-high dose systemic corticosteroids would usually be considered for HP patients with features of inflammation (e.g., GGO on HRCT, BAL lymphocytosis, well-documented exposure with acute or sub-acute symptom onset).
  3. There is case series-level evidence only for third-line agents including rituximab in HP.

DOI: 10.1111/resp.14847

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