Case Presentation: A 19-year-old man with a history of Chlamydia infection presented with lower extremity swelling, rash, arthralgia and fever for 6 days. He initially noticed pain and swelling localized to the left anterior shin which then spread to the left hip and left shoulder. He was sexually active with multiple female partners with inconsistent condom use, and denied toxic habits, recent travel or animal contact. He was born in the US and adherent with routine vaccinations. He appeared nontoxic and had low-grade fever. The left shin had an erythematous area with pitting edema. Tenderness and decreased range of motion were noted on left knee, hip and shoulder. Labwork was significant for a leukocytosis of 16,500 /µL with 81% neutrophils. Testing for influenza virus, parvovirus, human immunodeficiency virus, hepatitis viruses, Epstein-Barr virus, chlamydia, gonorrhea and Lyme disease was negative. Antinuclear antibody, rheumatoid factor, complements and cryoglobulin were normal. Magnetic resonance imaging of the left shoulder showed subacromial and subdeltoid bursitis with supraspinatus tendinitis and an anterior labral tear. Blood cultures grew Haemophilus influenzae serotype e (Hie) biotype 4. A transesophageal echocardiogram showed no vegetations, and there was no apparent underlying illness that precipitated the Hie infection. Treatment with intravenous ceftriaxone improved his symptoms and joint mobility. He was discharged to complete a total 21 days of antibiotics with oral levofloxacin.

Discussion: We describe a rare case of an immunocompetent young man who suffered an invasive infection due to Hie. H. influenzae is a gram-negative coccobacillus, isolated primarily from the human respiratory tract. It has 6 typeable strains (serotypes a-f) with a capsule and nontypeable strains which lack a capsule. H. influenzae serotype b (Hib) is the most virulent serotype, responsible for >80% of all invasive infections previously. Epidemiologic data have suggested that widespread Hib vaccination has contributed to a rise in invasive disease due to other typeable and nontypeable strains. Hie has been reported to cause pneumonia, bacteremia, meningitis, endocarditis, cellulitis, septic arthritis and hepatobiliary infection but not septic bursitis or tendinitis to our knowledge. While there are case reports of infection in healthy adults, invasive infection typically occurs in patients who are at extremes of age, immunocompromised or with anatomical abnormalities. As such, it would be prudent to look for underlying immune deficiency, malignancy or other undiagnosed conditions in patients with invasive infection due to non-serotype b H. influenzae.

Conclusions: H. influenzae serotype e can cause septic bursitis and tendinitis in a young, apparently healthy individual. Evaluation for underlying conditions would be reasonable for invasive infection due to non-serotype b H. influenzae.