Idiopathic pulmonary fibrosis (IPF) is usually chronic and progressive. Respiratory failure that occurs during the course of the disease is called acute exacerbation of IPF (AE-IPF), which may be caused by infection. Most published studies that explore the causes of acute IPF attacks focus on viral infection rather than bacterial infection sources. To our knowledge, there have been no previous reports of whooping cough as a pathogenic factor of AE-IPF. In this article, scholars from Japan report experience in two cases of AE-IPF caused by acute pertussis infection.
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case1
patient, male, 69 years old, was diagnosed with IPF five years before this acute exacerbation. The main complaints are in labor respiratory distress and dry cough. Physical examination showed that both lungs were fine and damp rales . The patient was admitted to the hospital due to sudden worsening of respiratory distress and was diagnosed with AE-IPF based on poor blood oxygen concentration and extensive new ground-glass shadows in both lungs (Figure 1). High levels of pertussis toxin (PT) antibody (147EU/mL) were found on the sample sampling on the first day of admission. After successful life-saving treatment, PT levels measured to 52 EU/mL 30 days after admission. The patient initiates long-term oxygen therapy (LTOT) and is discharged from the hospital and returned home.
Figure 1
cases 2
patient, male, 57 years old, was diagnosed with IPF 5 years ago, and is currently receiving LTOT oral Nidanib treatment. The patient was admitted to the hospital due to respiratory distress and worsening cough. Physical examination showed fine damp rales on both lungs. In addition, the patient had poor blood oxygen concentration, and CT scans showed extensive new ground-glass shadows in both lungs and were diagnosed as AE-IPF (Figure 2). According to the measurements on day 13 of the hospital admission, the patient showed high PT antibody titers (104 EU/mL). After successful clinical treatment, the patient returned home by increasing the LTOT dose.
Figure 2
Since adolescence, neither patient has received any whooping cough vaccine. Because it shows a typical common interstitial pneumonia pattern on high-resolution CT, it is clinically diagnosed as IPF. No blood tests or physical examinations showed any signs of autoimmune disease. Both patients reported chronic coughs associated with IPF, but uncontrollable worsening and persistent cough began to occur about 3 weeks before hospitalization. Neither of the patients detected pertussis from the sputum; in addition, no PCR analysis was performed, so the patient had no direct evidence to show the presence of the pathogen. Although no typical symptoms of pertussis were observed in any patient (e.g., chicken crowing inhalation roar), infectious diseases other than pertussis were detected by the sputum culture test or serum markers. No other pathogenic bacteria were detected in urine antigen tests or sputum culture tests. Furthermore, no heart failure was observed in any patient. Both patients received macrolide drugs and broad-spectrum beta-lactam antibiotics and received high-dose glucocorticoids.
Discussion and Conclusion
This report describes cases that demonstrate infection with pertussis as a cause of AE-IPF. Infection is currently considered to be the main pathogenic factor in AE-IPF. Although various bacteria and viruses have been studied as potential causes of AE-IPF infection, to our knowledge, the case presented here is the first document of pertussis as a pathogen causing AE-IPF.
This case report reveals three main findings. The first finding is that care should be taken into account for pertussis infection as part of the differential diagnosis during AE-IPF. Many doctors mistakenly believe that whooping cough only occurs when children are infected; however, recent literature suggests that whooping cough is now common in adults and is often overlooked by physicians. In addition, many adult cases of whooping cough have no typical symptoms, and IPF patients often present with persistent dry cough; therefore, during differential diagnosis, some doctors may not consider whooping cough at first. In the case of AE-IPF, these factors contribute to pertussis as a potential pathogen may often be overlooked.
The second finding is the expected efficacy of macrolide antibiotic treatment. While further discussion may be needed, macrolide antibiotic treatment can sometimes reduce the duration or severity of symptoms of pertussis infection. When patients exhibit AE-IPF, we do not routinely prescribe macrolide antibiotics known to be useful for pertussis.Therefore, our clinical experience may affect antibiotic selection in AE-IPF cases, as the current patient's AE-IPF may be caused by pertussis infection.
Finally, most respiratory bacterial infections are unpreventable; however, whooping cough is one of the few pathogens that can be prevented by vaccination. Many developed countries now recommend vaccination for whooping cough.
This case diagnosed pertussis infection based on serological testing; it is worth noting that serological diagnostic methods have been verified in several previous reports. The main diagnostic criteria for recent or currently active pertussis infection is PT antibody level 100EU/mL at any time point; both cases in the article meet this criteria.
Although the widespread vaccination of the pertussis vaccine has resulted in a sharp decline in the number of affected patients, recent reports of the increase in the number of pertussis cases in countries around the world are attracting attention. Therefore, studies focusing on AE-IPF that may be induced by pertussis may have important implications in the future.
The mechanism of AE-IPF inducing pertussis infection is not yet known. Pathogenic Bacillus pertussis is known to destroy bronchial epithelial cells, thereby inducing inflammatory cytokines and chemokines.
Source: Kuniaki Hirai; Tetsuya Homma; Acute Exacerbation of Idiopathic Pulmonary Fibrosis Induced by Pertussis.BMC Pulm Med. 2019;19(15).
