Discussion
This study represents a report of case that substantiates the airway casts produced by a toddler with preterm birth history and asthma. On physical exam, wheezing, decreased breath sounds and respiratory distress were observed in this patient. After treatment with inhaled budesonide, ipratropium bromide, terbutaline and nebulized N-acetylcysteine, the patient spontaneously expectorated casts without bronchoscopy.
Plastic bronchitis is an uncommon condition, characterized by the formation of tracheobronchial airway casts, which are partially or fully block the bronchial lumen. It is mainly associated with underlying congenital heart disease or lung diseases5. As to lung diseases, it has been associated with asthma, allergic bronchopulmonary aspergillosis, mycoplasma pneumoniae,influenza B virus infection and pulmonary tuberculosis, etc6-8. Clinically, patient with plastic bronchitis presents with dyspnea, wheezing, or pleuritic chest pain, and may have fever. Chest x-ray and CT findings are often non-specific including opacity or infiltrate 9,10.
The mechanism of casts’ formation remains unclear for the inflammatory casts in lung disease. In patients with asthma, previous studies hypothesis that the cause of casts is likely related to chronic inflammation and its attendant neutrophilic and eosinophilic airway infiltration, with decreased mucociliary clearance, the airways become occluded with eosinophils and neutrophils in a mucinous background9,11. There have been several case reports of plastic bronchitis caused by mycoplasma pneumoniae8,12. In this case, four weeks before this acute episode, the chest X-ray was normal, indicating the acute infection was the precipitating factor. The disease onset was in the autumn with low to moderate grade of fever. The blood routine examination was normal, and the application of macrolide anti-infection was effective. Thus, we consider the high possibility of mycoplasma pneumoniae infection in this case, in spite of the antibody was negative which may result from the earlier sample time on the third day of disease onset.
During the 24 to 38 weeks of gestation age,which is the saccular phase of lung development, the relationships between the air spaces, capillaries, and mesenchyme takes on more significance13. The alveolocapillary membrane is sufficient to participate in gas exchange until approximately 24 weeks of gestation age. For the very low birth weight infants (with birth weight less than 1500g) as this case or the other, are at higher risk because they have very few vessels and alveoli developed at birth. The pulmonary inflammatory response may have been initiated in utero, in the setting of chorioamnionitis. Chorioamnionitis is acute inflammation of the membranes and chorion of the placenta, commonly due to ascending polymicrobial bacterial infection, which leads to preterm premature rupture of membranes (pPROM). The earlier and more serious the exposure to chorioamnionitis is, the more immature and disrupted the lung structure would be14,15. The initiation of inflammation appears to cause impairment of the growth of alveoli and of the microvasculature. The boy’s mother had got pPROM and chorioamnionitis, which may disrupt the offspring’s lung alveolarization and vascularization during infancy and childhood.
Wheezing was related to degree of premature birth, increased gestation should improve the infant’s respiratory health up to 2 years of age16. Recurrent wheeze in infants and toddlers is associated with small airway calibre, low lung function and airway inflammation17. In this case, the potential impaired pulmonary function and the acute attack triggering by infection may play important roles in the plastic bronchitis.
On the treatment18,flexible or rigid bronchoscopy is most often used for cast removal. Other medication options include aerosolized fibrinolytics, such as urokinase, and inhaled mucolytics, such as acetylcysteine and dornase alfa. Mucolytics appear to be more useful in inflammatory casts, as the mucus contains. In those with lung diseases involving bronchial hyper-reactivity, treatment is based on the use of inhaled and systemic corticosteroids. In this case,the spontaneous expulsion of casts could prove effectively more flexible plugs, and the inhaled N-acetylcysteine also played a role19.
In conclusion, we report an exceptional case of a toddler born prematurely provoked plastic bronchitis. In the recurrent attacks of wheezing toddlers, the acute respiratory tract infection disturbs the airway barrier and may induce bronchial plastics, especially in those born prematurely.