Acromioclavicular septic arthritis: a case report of a novel pathogen.

In immunocompetent patients, septic arthritis of the acromioclavicular (AC) joint is a rare entity. It can be difficult to discern from glenohumeral septic arthritis and AC joint impingement syndrome. The usual symptoms are fever, erythema, swelling, palpable pain over the AC joint, and pain with shoulder motion. The most commonly reported causative organism is a Staphylococcus or Streptococcus species. Haemophilus parainfluenzae is a rare cause of septic arthritis in any joint. Although limited to case reports in the literature, most H parainfluenzae skeletal infections occur after surgical intervention. To our knowledge, this is the first case report of AC septic arthritis with H parainfluenzae.