Report Describes Rare Case of Acute Interstitial Pneumonia Triggered After Half Marathon

A 48-year-old woman with acute interstitial pneumonia (AIP), a rare and severe form of idiopathic interstitial lung disease, was successfully treated with high-dose corticosteroids and mycophenolate mofetil, according to a paper published in Respiratory Medicine Case Reports.

Investigators from Slovenia discussed the case of the previously healthy woman, who presented with acute shortness of breath and respiratory failure just 3 days after she ran a half marathon. The woman had a fever, chills, and muscle pain; she was originally treated with azithromycin but did not improve, the authors said. She also developed a dry cough and came to the hospital 7 days after the half-marathon.

AIP is typically indistinguishable from other acute respiratory diseases (ARDS) and requires histological confirmation. This case of AIP was seemingly triggered by strenuous physical exercise, the authors said, and was identified as AIP because of its signature lack of identifiable cause or predisposing condition.

The investigators administered amoxicillin plus clavulanic acid after noticing bilateral opacities on chest radiograph, they said. However, the patient’s condition deteriorated. On the fourth day in the hospital, the patient’s CT showed bilateral ground glass opacities and alveolar consolidations. EKG was normal and the patient tested negative for bronchoscopically obtained microbiological samples, they added. They did not attempt a transbronchial biopsy due to the patient’s respiratory failure, they wrote.

The patient met the criteria for ARDS but the authors made a presumptive diagnosis of AIP, as no other diagnosis seemed to be an alternative. They said that cryptogenic organizing pneumonia (COP) could not be ruled out, but diagnoses of COP are often delayed by 6 weeks or longer.

Next, the patient received intravenous therapy with combination piperacillin/tazobactam and methylprednisolone at an initial dose of 125 mg a day, but her condition continued to deteriorate. The investigators administered pulses of methylprednisolone (1000 mg) for 5 days and followed that up with a gradual tapering, they said, which showed partial improvement. Oxygen therapy was required for the patient and at this point, opacities remained present on the CT.

The investigators then tried mycophenolate mofetil twice daily 500 mg with an increase to 1000 mg twice daily. They observed gradual improvement from the patient and oxygen therapy was discontinued.

The study authors wrote that after 12 months since disease onset, there was significant reduction of opacities on the chest radiograph and CT. Lung function tests were normal for forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV₁), they added.

Nothing in the existing literature suggested strenuous exercise as a cause for ARDS or AIP, the study authors said, but they did encounter reports of pulmonary edema induced by marathon running. One paper showed that hemodynamic changes during exercise could be responsible for pulmonary edema, the study authors said, but mechanical stress or electrolyte disruptions could also play a role.

“Dysregulation of normal hemodynamic or immunological response may have played a role in the development of the lung pathology in our case,” the study authors wrote.

While mycophenolate mofetil is occasionally used to treat nonspecific interstitial pneumonia, there are no reports in the literature regarding its use for AIP, said the authors said suggest further research into the efficacy of MMF for AIP.

Reference

Markoska F, Lestan D, Turel M, Harkander M. Acute interstitial pneumonia triggered by strenuous exercise [published online May 7, 2020].

Respir Med Case Rep. doi:10.1016/j.rmcr.2020.101077.