A wide, epidemic outbreak of M. pneumoniae pneumonia occurred throughout Korea in late 2003. Compared with previous years, the 2003 outbreak resulted in more severe cases and in an increased incidence of extrapulmonary symptoms and/or complications. We compared the clinical characteristics for M. pneumoniae pneumonia of 2003 to those of the past years.

One hundred six children diagnosed with M. pneumoniae pneumonia by serologic tests at Bundang Cha General Hospital between Aug 2003 to April 2004 were enrolled. Medical records were reviewed retrospectively, for clinical, laboratory and radiological aspect as well as complications. The pleural effusions of 3 patients who underwent thoracentesis were also analyzed.

The duration of fever, cough, rhinorrhea, and sore throat was 8.2±4.7, 22.1±4.8, 8.4±2.1, 4.3±1.2 days, respectively. The incidence (percentage) and duration of abdominal pain, vomiting, diarrhea, headache, skin rash, arthralgia was 5.1±2.5 (21.9%), 3.4±2.1 (17.1%), 4.3±1.8 (16.2%), 3.5±2.1 (14.4%), 5.5±0.7 (5.9%) and 4.6±1.3 days (4.9%), respectively. The mean duration of admission and treatment were 7.4±4.3 days and 21.6±11.1 days. Higher values of CRP and ESR on admission were positively correlated with the duration of fever and length of admission. The findings of pleural effusion were similar to those seen in TB pleurisy. Complications, including myocarditis (2 cases), arthritis (3 cases), vasculitis (5 cases), asthma (3 cases), ARDS (1 case), and DIC (2 cases) were observed in 14.1% of patients.

We found a number of characteristics of M. pneumoniae pneumonia among cases from late 2003 that were different from those of previous years. This outbreak resulted in more severe cases and in an increased incidence of extrapulmonary symptoms and/or complications. A multicenter study is needed to verify the changes in clinical characteristics observed during the 2003 outbreak from previous ones.