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

Fibrotic Hypersensitivity Pneumonitis: What to Do When Immunosuppressive Therapy Fails to Stabilise Lung Function

Clinical Scenario

This protocol covers bird fancier's lung presenting as hypersensitivity pneumonitis with radiological and/or histopathological pulmonary fibrosis — the fibrotic phenotype. International diagnostic guidelines classify HP into fibrotic and nonfibrotic phenotypes based on the presence of fibrosis, which carries distinct prognostic and treatment implications.

Previous Treatment: Goal Not Achieved

The prior treatment line — immunosuppressive therapy (corticosteroids combined with a steroid-sparing agent) used when both inflammatory and fibrotic clinical features were present — did not achieve its target: stabilisation of lung function and slowing of FVC decline. Patients with fibrotic HP who progress despite antigen remediation, with or without immunosuppression, are considered to have progressive pulmonary fibrosis (PPF) disease behaviour. This protocol addresses the next step for that situation.

Next-Line Treatment Approach

For fibrotic HP that progresses after immunosuppressive therapy, the management approach shifts to antifibrotic therapy. The specific agents and full regimen are detailed in the complete protocol.

Treatment goal: Reduction in the rate of forced vital capacity (FVC) decline at 52 weeks.
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References

DOI: 10.1111/resp.14847

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.

Patients with fibrotic HP who progress despite antigen remediation, with or without immunosuppression, are considered to have PPF disease behaviour.

In such cases, there is good evidence for the introduction of antifibrotic therapy, as supported by the ATS/ERS/JRS/ALAT clinical guidelines for PPF.

Both nintedanib and pirfenidone have had regulatory body approval and subsidization for the indication of IPF in Australia and New Zealand for several years.

The INBUILD trial recruited patients with progressive fibrosing ILDs other than IPF (including fibrotic HP), demonstrating reduction in the rate of FVC decline in the nintedanib arm compared to placebo at 52 weeks, with a similar efficacy to IPF.

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