Neuroendocrine Cell Hyperplasia in Plastic Bronchitis: Cause, Effect or Incidental Finding?

Introduction: Plastic bronchitis (PB) is a rare disorder characterised by the development of large branching casts of mucus, cells and fibrin, alone or combination. Casts typically cause large airway obstruction, sometimes requiring bronchoscopic removal. Reported mortality rates vary from 6% to 60%, with higher rates in patients with underlying cardiac disease.

Case Report: We present the case of a previously well child presenting with a protracted history of recurrent acute presentations of airway obstruction from infancy. When well, bronchoscopy and chest imaging were normal. Episodes of airway obstruction, reportedly triggered by strong odours, were refractory to standard therapies and only resolved on expectoration of mucus plugs or casts. A diagnosis of idiopathic plastic bronchitis was made based on the clinical picture but there was no response to pulsed intravenous methylprednisolone, inhaled nebulised N-acetyl-cysteine, dornase alpha, tiotropium bromide, terbutaline or nedocromil. Cytology of casts shoed sheets of mature neutrophils and lung biopsy showed a mild eosinophilic bronchiolitis with an unexpected finding of neuroendocrine cell hyperplasia.

Discussion: Here we report on a girl with a unique airway disease, characterised by (1) chronic eosinophilic airway inflammation and increased airway neuroendocrine cells; and (2) recurrent acute neutrophilic airway inflammation with bronchial cast formation. Although there is evidence of airway eosinophilia, which might suggest allergic disease, the neutrophilic cytology of the casts in the acute attacks are against this hypothesis. Furthermore, no evidence of any significant allergic sensitization could be found. We speculate that this may be a late manifestation of neuroendocrine cell hyperplasia of infancy. It is interesting to speculate that these acute attacks may represent a disordered and immature airway response to noxious stimuli. The improvement in severity over time is supportive of this assertion.