P209 Where is the air coming from? Pneumomediastinum in a patient with granulomatosis with polyangiitis

Background/Aims We present the case of a 20-year-old female, who complained of a two-day history of sudden onset of global facial swelling worse in the morning, deterioration of nasal obstruction, frontal headache, found to have emphysema in the mediastinum and the neck. She was recently diagnosed with granulomatosis with polyangiitis on the basis of mild sensorineural hearing loss, extensive nasal crusting with sanguinolent discharge, myalgia, arthralgia and weight loss (10kg). Confirmed large nasal septum perforation and associated granulation via nasoendoscopy. Histology showed granulation tissue with polymorphs in the eosinophils in addition to positive immunology: C-ANCA 1:40, PR3 28. Her current treatment includes prednisolone, bone and gastric protection. She reduced her prednisolone from 50 mg to 25 mg and her facial swelling started, which led to the initial thought to be related to her prednisolone, therefore increased to 40 mg. Methods On admission, she was afebrile, tachycardic 108 per minute, saturation 99%, mild facial swelling, airways was patent, tenderness in maxillary sinuses, cardiopulmonary and abdominal examination were unremarkable. No neurology deficit. Laboratory revealed raised white cells 25 (109/L) C-reactive protein (CRP) 45 mg/L, rest unremarkable. A CT sinuses showed extensive sinonasal mucosal thickening and sinusitis, erosion of the nasal septum and free gas in the parapharyngeal, masticator and carotid spaces bilaterally, which may be due to cellulitis or fasciitis. She was started on Co-amoxiclav. Her scans were reviewed at the radiology meeting and subsequently assess for surgical emphysema and urgent investigations for collection or perforation. Results CT head, neck and thorax with contrast were performed and demonstrated air in the mediastinum and the neck extending from the level of the carina to the base of skull. There was no obvious lung abnormality or adenopathy. She remained haemodynamically stable, without respiratory distress. Coryzal symptoms persisted but other symptoms improved since her steroids were increased. Further assessments were performed, repeat nasal endoscopy showed septal perforation, significant inflammation, unable to visualise post-nasal space. Followed by maxillofacial review, ruling out dental abscess as origin of her emphysema. Respiratory review, no pneumothorax or intrinsic lung pathology. Additionally, a gastromiro was performed which ruled out perforation. Conclusion She completed a week of intravenous antibiotics then discharged on prednisolone whilst being screened for rituximab. Unfortunately, she was readmitted with shortness of breath secondary to her severe bilateral nostril obstruction, upper airway granulation. A repeat chest XR did not show evidence of pneumomediastinum or pneumothorax. She was then started on rituximab as inpatient and currently continues reducing her prednisolone with good response. Interestingly despite thorough investigations, there was no source of air leaking found, a final diagnosis of possible pneumomediastinum as rare manifestation of granulomatosis with polyangiitis was made after excluding the other causes, few cases described. Disclosure A. Escudero Siosi: None. P. Sharma: None. A. Chan: None.