Thigh abscess due to haemophilus influenzae type f in a human immunodeficiency virus-positive child

The widespread use of the Haemophilus influenzae serotype b conjugate vaccine in developed countries has led to a dramatic reduction in invasive disease because of that serotype. The H. influenzae serotype b vaccine provides no significant protection against nontypeable or non-b encapsulated strains. Invasive disease due to H. influenzae serotype f (Hif) remains uncommon in children, although a higher incidence is reported in those with chronic disease and/or immunodeficiency. We report the case of a 5-year-old female patient with human immunodeficiency virus infection who developed a large thigh abscess and cellulitis because of Hif. The case illustrates an unusual presentation of invasive Hif infection and reiterates the need to consider uncommon pathogens as etiological agents in disease presenting in immunocompromised hosts.