Fever Persistent for 15 Days: Not Typical of HP or IPF
Neither hypersensitivity pneumonitis (HP) nor idiopathic pulmonary fibrosis (IPF) typically manifest with persistent fever lasting 15 days, and such prolonged fever should prompt investigation for alternative diagnoses including infection, malignancy, or other systemic conditions.
Acute Hypersensitivity Pneumonitis
- Acute HP can present with fever, but it is typically transient and episodic rather than persistent for 15 days 1, 2, 3
- Fever in acute HP occurs 4-8 hours after antigen exposure and is accompanied by chills, myalgias, cough, and dyspnea, resembling an influenza-like illness 3
- These acute episodes are recurrent and temporally related to exposure, not continuously present for extended periods 3
- The fever resolves with antigen avoidance and recurs with re-exposure, creating an intermittent pattern rather than persistent fever 2
Chronic/Fibrotic Hypersensitivity Pneumonitis
- Chronic HP typically lacks fever entirely 3
- Patients with chronic HP present with insidious onset of cough, dyspnea, fatigue, and weight loss without the systemic inflammatory features seen in acute disease 4, 1
- The absence of acute episodes is common in chronic HP, with patients reporting gradual symptom progression rather than febrile illnesses 4
Idiopathic Pulmonary Fibrosis
- IPF does not present with fever as a characteristic feature 5
- IPF manifests with progressive dyspnea, cough, and restrictive physiology without systemic inflammatory symptoms 5
- Male sex, age >60 years, and smoking history are the distinguishing clinical features of IPF, not fever 5
Clinical Implications
Persistent fever for 15 days in a patient with interstitial lung disease findings should raise suspicion for:
- Infectious pneumonitis (bacterial, fungal, or atypical organisms)
- Drug-induced lung disease with systemic features
- Connective tissue disease-associated ILD with active systemic inflammation
- Organizing pneumonia
- Malignancy
The diagnostic workup should prioritize excluding infection and other systemic causes before attributing symptoms to HP or IPF 6
If HP is still suspected despite prolonged fever, consider that the patient may have a superimposed infection or alternative diagnosis requiring multidisciplinary discussion 6