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.