Human parainfluenza virus type 3 (HPIV 3) community-acquired pneumonia (CAP) mimicking pertussis in an adult: The diagnostic importance of hoarseness and monocytosis

Background are relatively few causes of acute community-acquired pneumonias (CAPs) in adults associated with prolonged cough. In adults the most common acute CAPs with a prominent and persistent nonproductive cough are due to Mycoplasma pneumoniae, Chlamydophilia (Chlamydia) pneumoniae, or Bordetella pertussis (pertussis). Pertussis is an underrecognized and underappreciated cause of CAP in adults. Different from classic pertussis in children, pertussis in adults presents with prolonged dry cough, that is, the “100-day cough.” In pertussis, the characteristic nonspecific laboratory findings are leukocytosis and relative lymphocytosis. Dry cough accompanied by hoarseness with CAP in an adult should suggest C. pneumoniae or a respiratory virus (eg, influenza, parainfluenza, respiratory syncytial virus). s sent the case of a young woman who presented with a prominent and persistent pertussis-like cough with hoarseness. She had no leukocytosis or relative lymphopenia, which argued against the diagnosis of pertussis. Notably, she had persistent monocytosis. Her protracted pertussis-like cough that persisted during her hospitalization was so impressive that the diagnostic impression was pertussis. Direct fluorescent antibody (FA) and throat cultures were negative for pertussis. Furthermore, her hoarseness suggested the possibility of C. pneumoniae, but her C. pneumoniae immunoglobulin-M titer was negative. s e C. pneumoniae was ruled out, her hoarseness suggested a respiratory viral cause. A respiratory FA viral panel and viral throat cultures were obtained. The respiratory FA viral panel was negative for influenza A/B, respiratory syncytial virus, metapneumovirus, adenovirus, cytomegalovirus, and parainfluenza viruses. However, her viral throat cultures grew parainfluenza virus type 3 (HPIV 3), confirming the diagnosis. sion best of our knowledge, this is the first case of HPIV 3 CAP presenting with a prominent and persistent pertussoid cough in an adult mimicking pertussis with hoarseness and monocytosis.