"Tree in bud" attributable to organising pneumonia

Learning point

Cryptogenic OP may rarely present as a small airway-predominant disease causing severe airflow limitation and a 'tree in bud' pattern on HR-CT.

A 19-year-old man presented with dyspnoea, a non-productive cough and subfebrile temperature. Chest radiography showed a diffuse nodular pattern and a pneumomediastinum. HR-CT revealed a diffuse 'tree in bud' pattern ( figure 1 ). An infectious bronchiolitis was suspected. Despite treatment with moxifloxacin he developed hypercapnic respiratory failure requiring mechanical ventilation. Extensive microbiological investigations did not reveal a pathogenic microorganism. Continued treatment with antibiotics, low-dose steroids and neomacrolides was not effective, and an open lung biopsy was performed. Histology showed an organising pneumonia (OP) with extensive endobronchiolar granulation tissue ( figure 2 ). The treatment was converted to high-dose steroids upon which the patient improved rapidly. Spirometry performed...