Across five nationwide outbreaks in Korea, early use of corticosteroids was observed to markedly lessen disease severity. In this investigation, we examined clinical and laboratory outcomes in 56 pediatric patients who were given corticosteroids early for pneumonia caused by either macrolide-resistant (M. pneumoniae, MRMP) or macrolide-sensitive (M. pneumoniae, MSMP) strains between July 2019 and February 2020. Every patient tested positive on both PCR and serological assays and received corticosteroids within 24–36 hours after hospital admission. Mutations at nucleotides 2063, 2064, and 2067 within domain V of 23S rRNA were detected. The participants had an average age of 6.8 years, with a male-to-female ratio of 1.2:1 (31 males, 25 females). A majority (73%) were infected with MRMP strains, all showing the A2063G transition. When comparing MRMP and MSMP groups treated with early, dosage-adjusted corticosteroids, no major differences were found in clinical presentation or laboratory results. Nonetheless, children whose fever lasted beyond 48 hours or showed rising biomarkers such as elevated lactate dehydrogenase after standard steroid therapy might require increased corticosteroid dosage.
