A 17-year-old girl with facial edema and weakness

A previously healthy 17-year-old adolescent initially presented to her dentist with right-sided facial swelling for 2 weeks. There was concern for an infected tooth which was extracted. Nevertheless, progression of facial edema ensued with recurrent fevers requiring admission to a community hospital where swabs of the tooth socket failed to identify a pathogen. Despite treatment with five suitable intravenous antibiotics over 3 weeks, she failed to improve. This resulted in transfer to our paediatric hospital. On admission, she reported dysphagia, weight loss and fatigue. Physical examination was significant for asymmetrical face and neck swelling with periorbital edema, periodontal gingival erythema and abnormal nail fold capillary pattern on capillaroscopy. She had a hoarse voice and significantly reduced proximal muscle strength. Oxford scale manual muscle testing was 2/5 proximally and 4/5 distally. There were no apparent rashes (Figure 1). Laboratory investigations are shown in Table 1. Head and neck magnetic resonance imaging revealed significant edema of the facial, neck and retropharyngeal muscles without venous thrombosis. Magnetic resonance imaging of the pelvic and shoulder girdles confirmed extensive subcutaneous and proximal muscle edema with deep and superficial fasciitis. Video fluoroscopy demonstrated weak pharyngeal and esophageal muscles. A muscle biopsy revealed the diagnosis