Haemophilus influenzae infection of an existing lung cyst.

Although Haemophilus influenzae is becoming recognized as a cause of serious pulmonary infections in adults, it has not been previously reported to infect lung cysts. We describe a 25-year-old man who had a lung cyst in which a serious infection developed. Both needle aspiration of the cyst and blood culture confirmed that the infection was caused by H influenzae.