Retropharyngeal abscess from an unusual organism-Kingella denitrificans-in a patient on low-dose methotrexate.

Retropharyngeal abscess can be a life-threatening emergency with potential for airway compromise. We report a case of retropharyngeal abscess caused by Kingella denitrificans in a 66-year-old Caucasian man taking low-dose methotrexate for psoriatic arthritis. K denitrificans has not been previously reported as a cause of retropharyngeal abscess. K denitrificans, along with other Kingella species, is often found to be part of the normal upper respiratory tract flora. Potentially life-threatening complications of retropharyngeal abscess can occur in immunocompromised patients. Although complications of immunosuppression are thought to be rare with the use of low-dose pulse methotrexate for non-neoplastic conditions, such complications with prolonged use of low-dose pulse methotrexate may be seen.