Acute tracheal trauma and chronic tracheal collapse in an asthmatic mature pony

A 17-year-old cross-bred pony gelding was presented for acute onset of respiratory distress and an inspiratory honking noise. He had been previously diagnosed with moderate mastocytic equine asthma and chronic tracheal collapse on endoscopy (grade 3/4). At admission, predominantly inspiratory dyspnoea with open mouth breathing, hypoxaemia and hypercapnia were present. Cervical and thoracic radiographs showed severe tracheal collapse from the mid-cervical region to the thoracic inlet and a moderate generalised bronchial pattern. Due to the poor prognosis, euthanasia was elected. On post-mortem examination, some granulomatous nodules compatible with tracheobronchopathia osteochondroplastica were present in the tracheal lumen, and the entire trachea was laterally flattened. This uncommon laterolateral collapse was more severe at the thoracic inlet and in the mid-cervical area, where a peritracheal haematoma was detected. A blunt trauma that exacerbated the tracheal collapse was suspected. Tracheal histology revealed degenerative changes. Degeneration of tracheal cartilage and connective tissue can be a predisposing factor to chronic collapse and recurrent episodes of inspiratory and expiratory distress. It is unknown whether chronic tracheal collapse is an independent condition or a consequence of an underlying lung disease.