Non-traumatic atlanto-axial subluxation (AAS) is an uncommon complication of upper neck inflammatory processes and head and neck surgery. It is also known under the eponym of Grisel's syndrome (GS). We present a case report of a 6-year-old boy with GS that resulted from a retropharyngeal abscess. A diagnosis was not made until 2 months after the occurrence of infection. Re-evaluation of repeated CT scans of the neck showed the sequential development of AAS. These findings implied that the pathogenesis of GS is a distention of the ligaments between the atlas and axis rather than loosening of the ligaments caused by the spread of an inflammatory edema from the soft tissues of the neck as has been proposed by others.

A 49-year-old woman treated with increasing dosage of propylthiouracil (PTU) in order to control hyperthyroidism, developed progressive necrotic ulcers in the oral cavity, oropharynx and rhinopharynx and vasculitic ulcers on both auricular pinnae after a few days. The PTU treatment was immediately discontinued and the mucosal and skin manifestations resolved promptly. Laboratory findings, including anti-neutrophil cytoplasmic antibodies (ANCA), suggested allergic vasculitis. This is to our knowledge the first reported case of oral manifestations of PTU-induced allergic vasculitis.