Background: Mycoplasma pneumoniae (MP) is a major cause of community-acquired pneumonia in children. Currently, no study exists regarding the frequency of the mycoplasmal antibody on Jeju Island. The aim of the present study was to investigate the frequency of mycoplasmal antibody among children living on Jeju Island.

Methods: From March 2009 to February 2011, the frequency of mycoplasmal antibody among 1580 pediatric (＜10 years old) patients who were tested for the mycoplasmal antibody titer in Cheju Halla Hospital were retrospectively investigated. The authors also analyzed the positive rates according to age, sex, and season.

Results: The frequency of mycoplasmal antibody titers were 69.4% for an antibody titer ＞1：40, 20.8% in an antibody titer ＞1：320, and 10.7% in an antibody titer ＞1：640. The positive rates of each antibody titer were lowest in children under the age of 6 months, and the positive rates increased gradually with age until 4 years, where the frequency showed a “plateau.” There were minor cyclic increases of positive rate (＞1：320, ＞1：640) every three months from August 2009 to June 2010, and there was a major increase of positive rate (＞1：320, ＞1：640) from July 2010 to January 2011. However, there was no positive rate cyclic pattern of mycoplasmal antibody in the lower titer (＞1：40) patients.

Conclusion: The frequency of mycoplasmal antibody titer is lowest under the age of 6 months. The positive rates rise gradually with age until the age of 4 years. The present study showed minor peaks of mycoplasmal antibody titer every three months and a major peak of mycoplasmal antibody titer. The results can be helpful for the interpretation and diagnosis of MP among pediatric patients on Jeju Island. (Korean J Clin Microbiol 2012;15:32-36)