ObjectiveTo investigate the possible correlation between changes in haemorheology and the HIF-1/EPO pathway in children with Mycoplasma pneumoniae pneumonia (MPP) to provide new ideas for the early clinical identification of hypercoagulability and reduce the incidence of thrombosis.MethodsA total of 205 children with newly diagnosed MPP were selected from our department and divided into a general MPP group (100 patients) and a severe MPP group (105 patients) according to diagnostic criteria. In addition, 30 healthy children were selected as the control group. Routine blood and coagulation function data were collected, and the expression levels of T-cell factors, HIF-1α, EPO and haemorheology were detected.ResultsThe levels of D-dimer, FDP and fibrinogen in the MPP group were significantly greater than those in the control group and more obvious in the severe group than in the general group. Compared with those in the control group, the whole blood viscosity (low, medium, high tangential), plasma viscosity, whole blood low tangential reductive viscosity and erythrocyte aggregation index in the haemorheology of children in the MPP group were significantly greater, and the range of increase in the severe group was greater than those in the general group. The red blood cell (RBC) count and haematocrit (HCT) of children in the MPP group were significantly greater than those in the control group at admission and were more altered in the severe group than in the general group. Moreover, the serum expression levels of TNF-a, IFN-γ, IL-6, IL-8, IL-10, IL-17, HIF-1α and EPO in the MPP group were significantly greater than those in the healthy control group. With the exception of IFN-γ, the cytokines levels in the severe group were significantly greater than those in the general group. The expression level of HIF-1α was significantly correlated with the elevated levels of TNF-a, IL-6 and IL-8.ConclusionHypercoagulability occurs during the course of MPP in children, especially those with severe disease. The increase in blood viscosity may be an important reason for hypercoagulability, and highly inflammatory cytokines such as TNF-a, IL-6 and IL-8 in children may increase the RBC and HCT levels by activating the HIF-1α/EPO pathway, which may lead to changes in haemorheology and thus participate in the development of hypercoagulability.