• Patient is ≥ 18 years of age

• IPF or IPF (likely) diagnosis defined on 2018 international recommendations

• Definite or suspected Acute Exacerbation defined by the international working group criteria after exclusion of alternative diagnoses of acute worsening

• \*The criteria of IPF-AE are as follows:

⁃ Previous or concurrent diagnosis of IPF (a)

⁃ Acute worsening or development of dyspnea typically \< 1-month duration

⁃ Computed tomography with new bilateral ground-glass opacity and/or consolidation superimposed on a background pattern consistent with usual interstitial pneumonia pattern (b)

⁃ Deterioration not fully explained by cardiac failure or fluid overload Patients who fail to meet all 4 criteria due to missing computed tomography should be considered as having suspected Acute Exacerbation.

∙ If the diagnosis of IPF is not previously established, this criterion can be met by the presence of radiologic and/or histopathologic changes consistent with usual interstitial pneumonia pattern on the current evaluation.

‣ If no previous computed tomography is available, the qualifier new can be dropped from the third criterion.

• For women of childbearing age: efficient contraception for the duration of the study\*

• \*Effective contraception is defined as any contraceptive method that is used consistently and appropriately and has a low failure rate (i.e., less than 1% per year)

• Affiliation to the social security

• Patient able to understand and sign a written informed consent form or in case of incapacity of the patient to a relative whom understand and sign a written informed consent form