Acute septic arthritis of the acromioclavicular joint caused by Haemophilus parainfluenzae: a rare causative origin

Septic arthritis of the acromioclavicular (AC) joint is a rare entity with symptoms that include erythema, swelling, and tenderness over the AC joint, fever, and limitation of shoulder motion with pain. In previous reports, Staphylococcus and Streptococcus species have been mentioned as common causative organisms. Haemophilus parainfluenzae is a normal inhabitant of the oral cavity, respiratory tract, gastrointestinal tract, and urogenital tract. However, it sometimes causes opportunistic infections leading to septic arthritis and osteomyelitis. AC joint infection associated with H.parainfluenzae is very rare, and only one case has been reported in the literature. Moreover, septic arthritis in immunocompetent patients is also very rare. Here, we report the case of a healthy patient with H. parainfluenzae-related septic arthritis of the AC joint.