Abstract
Haemophilus parainfluenzae, a HACEK organism, is one of five species known to less commonly cause infective endocarditis. This article presents a rare and noteworthy case of H. parainfluenzae endocarditis affecting the aortic valve, seemingly unique when Haemophilus species in endocarditis were previously known to more commonly involve the pulmonic or mitral valves. In the setting of H. parainfluenzae bacteremia, a 61-year-old male with no significant past medical history exhibited subtle systemic symptoms with a paucity of clinical signs associated with endocarditis and no evidence of embolic disease. A thorough workup demonstrated a large vegetation involving the aortic valve causing acute aortic insufficiency necessitating subsequent replacement of the aortic valve. In follow-up appointments with providers, the patient demonstrated excellent recovery returning to his baseline activity within 6 months. This case highlights the importance of considering endocarditis in Haemophilus bacteremia, especially in those with an unclear source of infection. Recognition of these rare presentations can assist with timely diagnosis and appropriate management, thus improving patient outcomes.