Management of refractory Mycoplasma pneumoniae pneumonia: utility of measuring serum lactate dehydrogenase level.

It has been suggested that cytokines are associated with refractory Mycoplasma pneumoniae pneumonia, and steroid administration is reported to be effective in this situation. In order to elucidate the characteristics of refractory M. pneumoniae pneumonia, we analyzed five pediatric patients with refractory M. pneumoniae pneumonia, which was defined as showing prolonged fever and deterioration of clinical and radiological findings despite administration of appropriate antibiotics, compared with 15 pediatric patients with M. pneumoniae pneumonia who responded to treatment promptly (control group). Serum lactate dehydrogenase (LDH), alanine aminotransferase (ALT), aspartate aminotransferase (AST), and interleukin (IL)-18 levels were significantly higher in the refractory group than in the control group at the initiation of corticosteroid use (LDH: 571 vs 292 IU/L, p = 0.0129; ALT: 25 vs 11 IU/L, p = 0.0143; AST: 41 vs 26 IU/L, p = 0.0404; IL-18: 579 vs 365 pg/mL, p = 0.0402). Significant correlation was found between serum values of IL-18 and LDH (r(2) = 0.504, p = 0.0433). The administration of corticosteroids to patients in the refractory group resulted in the rapid improvement of symptoms and decrease in serum LDH levels in all patients. A serum LDH level of ≥410 IU/L, which was calculated from receiver operating characteristic curve analysis, seemed to be an appropriate criterion for the initiation of steroid therapy. In conclusion, serum IL-18 and LDH levels can be used as parameters to determine which patients are candidates for corticosteroid therapy. In addition, serum LDH levels seem to be a useful marker for the evaluation of therapeutic efficacy in refractory M. pneumoniae pneumonia.