Infectious arthritis due to Hemophilus influenzae

A healthy 51-year-old male developed multiarticular infectious arthritis due to Hemophilus influenzae, a rare cause of infectious arthritis in adults. Previous case reports are reviewed. Predisposing factors include chronic illness, underlying joint disease, joint trauma, and respiratory infection. H. influenzae is frequently misidentified on Gram stain, being mistaken for gonococci or pneumococci. Infections due to H. influenzae may occur in normal adults. Aspects of immunity are discussed.