Objective  To explore the association between the levels of plasma D-dimer and the disease severity and prognosis of Mycoplasma pneumoniae pneumonia (MPP) in children

  Methods  We retrospectively analyzed the clinical data of pediatric MPP patients who were admitted in our hospital between January 1, 2016 and December 31, 2018. According to the peak value of D-dimer, patients were divided into the normal group (D-dimer<0.55 mg/L) and the elevated group (D-dimer≥0.55 mg/L). Information regarding the demographics, clinical manifestations, auxiliary examinations and treatments of patients in the two groups was compared.

  Results   Of the 231 MPP patients included in the study, 70 were in the normal group and 161 were in the elevated group. The age of patients in the D-dimer elevated group was significantly higher than that of the normal group (P<0.01). Compared with the normal group, the elevated group had longer lengths of fever, hospital stay and antibiotic therapy, and more severe radiographic manifestations (all P<0.01). In addition, the incidence of extrapulmonary complications, refractory MPP and severe MPP in the elevated group were significantly higher than those in the normal group (P<0.01). As for the laboratory data, we found that neutrophils, C-reactive protein, lactate dehydrogenase, interleukin-6, interleukin-10 and interferon-γ were significantly higher in the elevated group than those in the normal group (P<0.05). After treatments, all patients showed improvement and were discharged, but the proportions of patients requiring glucocorticoids, bronchoscopy, thoracentesis were significantly higher in the elevated group than those in the normal group (P<0.05). Follow-up findings showed that the absorption rate of lung lesions 4 weeks after admission was significantly higher, the time needed for lung lesions absorption was significantly shorter, and the incidence of pulmonary sequelae was significantly lower in the normal group than those in the elevated group (all P<0.05). Correlation analysis showed that D-dimer level was positively correlated with the severity of pneumonia (r=0.272, P=0.000) and the incidence of pulmonary sequelae (r=0.235, P=0.000).

  Conclusion  Pediatric patients of MPP who had elevated plasma D-dimer had clinical manifestations that were more severe, required longer duration of treatment and longer recovery time for lung lesions, and were more likely to have pulmonary sequelae.