Abstract: 　Objective　To explore the clinical characteristics and prognosis of severe Mycoplasma pneumoniae pneumonia (SMPP) with pleural effusion. Methods　The clinical data of SMPP with pleural effusion in 46 children and SMPP without pleural effusion in 53 children were retrospectively analyzed and compared. Results　Compared with SMPP without pleural effusion group, male to female sex ratio and the proportions of pulmonary atelectasis, extrapulmonary system damage and systemic glucocorticoid use were significantly increased. The days of hospitalization, days of fever, the effective time of azithromycin and the absorption time of pulmonary lesions after discharge were all significantly prolonged. The levels of C-reactive protein, PCT, D-dimer and lactate dehydrogenase were significantly increased. The level of albumin was significantly decreased in SMPP with pleural effusion group. The differences were statistically significant (P<0.05). Compared with the low-medium volume of pleural effusion group, the children in the high volume of pleural effusion group were older and had significantly longer duration of fever and hospitalization, and differences were statistically significant (P<0.05). The age of children with MP positive hydrothorax was significantly higher than that of children with MP negative hydrothorax (P<0.05). The levels of D-dimer and LDH in children having intrinsic airway secretory status rating > 4 were higher than those in children having intrinsic airway secretory status rating ≤ 4 (P<0.05) in SMPP children with pleural effusion. Conclusions　Children with SMPP combined with pleural effusion have a longer duration of fever, a higher incidence of extrapulmonary and intrapulmonary complications, significantly abnormal serum inflammatory indicators and blood biochemical indicators, and later start time of effectiveness of azithromycin alone and a longer absorption time of pulmonary lesions. The possibility of systemic glucocorticoid application should be predicted as early as possible in the acute phase and regular follow-up of chest imaging is required after discharge.

Key words: Mycoplasma pneumoniae pneumonia;　 pleural effusion; follow-up; 　prognosis;　 child