Properdin deficiency associated with recurrent otitis media and pneumonia, and identification of male carrier with Klinefelter syndrome

Properdin is an initiator and stabilizer of the alternative complement activation pathway (AP). Deficiency of properdin is a rare X-linked condition characterized by increased susceptibility to infection with Neisseria meningitidis associated with a high mortality rate. We report properdin deficiency in a large Pakistani family. The index cases were found by screening for immunodeficiency due to a history of recurrent infections. This revealed absent AP activity, but normal classical and lectin pathway activity. Sequencing of the properdin gene (PFC) revealed a novel frameshift mutation. When all available relatives (n = 24) were screened for the mutation, four affected males, four female carriers and a male heterozygous carrier were identified. He was subsequently diagnosed with Klinefelter syndrome. A questionnaire revealed a striking association between properdin deficiency and recurrent otitis media (P = 0.0012), as well as recurrent pneumonia (P = 0.0017). tudy is the first to show a significant association between properdin deficiency and recurrent infections.