Comparative analysis of blood routine, C-reactive protein, and biochemical markers in children with Mycoplasma pneumoniae pneumonia and its coinfections

Introduction Mycoplasma pneumoniae pneumonia (MPP) is a common cause of pediatric community-acquired pneumonia, and coinfections with Haemophilus influenzae (Hi) or influenza virus may alter disease severity. Identifying distinct laboratory patterns may help clinicians recognise coinfections early. Methods A retrospective analysis was conducted on 140 hospitalized children with confirmed MPP (2014–2024). Patients were grouped as MPP alone ( n = 64), MPP+Hi ( n = 36), and MPP+influenza ( n = 40). Clinical characteristics, complete blood count (CBC), hypersensitive C-reactive protein (hs-CRP), and biochemical indicators (ALT, AST, CK, CK-MB, urea, creatinine) were compared among groups. Correlation analyses were performed for biochemical markers. Results Children with MPP+Hi showed the highest hs-CRP levels (23.93 ± 21.26 mg/L), longest fever duration, and longest hospital stay. The MPP+influenza group had significantly lower WBC (7.25 ± 3.50 × 10 9 /L) and platelet counts (266.00 ± 97.46 × 10 9 /L), and a higher monocyte percentage (10.18 ± 3.29%). Simple MPP cases had the highest lymphocyte percentage. No group differences were found in ALT, AST, CK, CK-MB, urea, or creatinine, although CK-MB was elevated across all groups. Correlation analysis showed weak but significant associations among AST, ALT, CK, and CK-MB. Conclusion Coinfection type influenced inflammatory and haematological patterns in children with MPP: Hi coinfection produced stronger inflammatory responses, while influenza coinfection showed viral-associated lymphopenia and thrombocytopenia. Routine laboratory parameters may support earlier recognition of coinfections and guide more targeted clinical management.