Mycoplasma pneumoniae pneumonia (MPP) is community-acquired pneumonia (CAP) occurring commonly in children in our country. The clinical features and treatment outcomes of MMP are thought to be closely associated with age and radiographic progression. However, studies have investigated the age-specific combined with radiographic features in patients with MPP are scarce.

We aimed to investigate the clinical manifestations in children with MPP at different ages and to determine the risk factors for lobar pneumonia so as to provide reference for its precise treatment.

This was a retrospective study. The clinical data of 895 children with MPP who were hospitalized at Department of Pediatrics, Hunan Provincial People's Hospital/The First Affiliated Hospital of Hunan Normal University between August 2023 and April 2024 were included in the study and divided into the group with aged <5 years old and the group with aged≥5 years old according to age. Different age groups were further divided into subgroups (lobar pneumonia and non-lobar pneumonia) according to the chest imaging findings. The clinical data, laboratory findings, treatments and outcomes were collected and analyzed. To use the method based on Taqman fluorescent probe RT-PCR for detecting MP-DNA and drug resistant gene. Multivariate Logistic regression models were used to identify the risk factors for lobar pneumonia.

Of the 895 patients with MPP we studied, 418 of whom (46.7%) were male, 477 of whom (53.3%) were female. The median age of the children was 7.1 years (interquartile range, 5.1 to 8.9). The clinical data of 218 (24.4%) patients with MPP aged <5 years old and further divided into the study subgroup with 164 (18.3%) cases (non-lobar pneumonia) and 54 (6.0%) cases (lobar pneumonia). The clinical data of 677 (75.6%) patients with MPP aged≥5 years old, and further divided into the study subgroup with 304 (34.0%) cases (non-lobar pneumonia) and 373 (41.7%) cases (lobar pneumonia). The proportion of female patients, age, cough, fever, decreased breath sounds, headache, dizziness, proportion of peak temperature≥39.0 ℃, proportion of sore throat, fever duration, neutrophil percentage, neutrophil-to-lymphocyte ratio (NLR), C-reactive protein, platelet-to-lymphocyte ratio (PLR), D-dimer level, proportion of mycoplasma pneumoniae (MP) resistance, proportion of bronchoalveolar lavage, proportion of methylprednisolone treatment, proportion of lobar pneumonia and length of hospital stay were higher in the≥5-year-old group than in the <5-year-old group. In contrast, the proportions of wheezing, rales, three-concave sign, white blood cell count (WBC), albumin, lactate dehydrogenase (LDH), glutamic transaminase level, intravenous immunoglobulin usage, non-invasive continuous positive airway pressure (CPAP) ventilation, proportion of nasal cannula oxygen therapy, and pediatric intensive care unit (PICU) admission were lower in the≥5-year-old group (all P<0.05). The median age, proportion of allergic constitution, proportion of heat peak ≥39.0 ℃, proportion of pulmonary respiratory sound attenuation, WBC and MP resistance, proportion of bronchoscopy, proportion of methylprednisolone treatment, and length of hospital stay in the <5-year-old non lobar pneumonia subgroup were higher than those in the <5-year-old non lobar pneumonia subgroup (P<0.05). In the≥5-year-old lobar pneumonia subgroup, the proportions of allergic constitution, fever peak≥39 ℃, proportion of decreased breath sounds, D-dimer, drug resistance, bronchoscopy, methylprednisolone, and length of hospital stay were higher than those in the≥5-year-old non-lobar pneumonia subgroup, while the proportions of wheezing, three-concave sign, and oxygen therapy were lower than those in the≥5-year-old non-lobar pneumonia subgroup, with statistically significant differences (P<0.05). Multivariate Logistic stepwise regression analysis showed that age≥5 years, allergic constitution, fever peak≥39.0 ℃, elevated NLR, and MP drug resistance were risk factors for lobar pneumonia (P<0.05).

The pulmonary signs in the <5-year-old age group are more obvious, requiring more oxygen therapy and PICU support; while the extrapulmonary symptoms in the≥5-year-old group are more prominent, with a longer hospital stay, prone to progression to lobar pneumonia, a high incidence of drug resistance, and more common needs for glucocorticoids and bronchoalveolar lavage treatment. Age≥5 years, allergic constitution, fever peak≥39.0 ℃, elevated NLR, and drug resistance are risk factors for the occurrence of lobar pneumonia.

肺炎支原体肺炎（MPP）是我国常见的儿童社区获得性肺炎，其临床特征及预后与年龄、影像学进展密切相关，但目前针对年龄分层联合影像学分析的系统研究仍然不足。

探讨不同年龄儿童MPP临床特征及发生大叶性肺炎的高危因素，为精准诊疗提供帮助。

回顾性纳入湖南省人民医院（湖南师范大学附属第一医院）儿童医学中心2023年8月—2024年4月收治的895例住院MPP患儿为研究对象，按年龄分为<5岁组和≥5岁组，按影像学结果进一步分为<5岁非大叶性肺炎亚组、<5岁大叶性肺炎亚组、≥5岁非大叶性肺炎亚组、≥5岁大叶性肺炎亚组，收集患者一般资料、实验室检查指标、治疗及预后资料，并比较组间差异。采用多重实时荧光定量PCR检测呼吸道病原体核酸，Taqman荧光探针PCR技术检测肺炎支原体（MP）核酸及耐药突变位点基因。采用多因素Logistic逐步回归分析探究发生大叶性肺炎的危险因素。

895例MPP患儿中，男418例（46.7%），女477例（53.3%），中位年龄为7.1（5.1，8.9）岁。<5岁组218例（24.4%），≥5岁组677例（75.6%）。<5岁非大叶性肺炎亚组164例（18.3%），<5岁大叶性肺炎亚组54例（6.0%），≥5岁非大叶性肺炎亚组304例（34.0%）、≥5岁大叶性肺炎亚组373例（41.7%）。≥5岁组患儿女性比例、年龄、咳嗽、发热、呼吸音减弱、头痛、头晕、热峰≥39.0 ℃、咽痛比例及热程、中性粒细胞百分比、中性粒细胞/淋巴细胞比值（NLR）、C反应蛋白、血小板计数/淋巴细胞比值（PLR）、D-二聚体水平、MP耐药比例、支气管肺泡灌洗比例、甲泼尼龙治疗比例、大叶性肺炎比例以及住院时间高于<5岁组，而喘息、啰音、三凹征比例、白细胞计数（WBC）、白蛋白、乳酸脱氢酶（LDH）、谷氨酸转移酶水平、丙种球蛋白的使用、鼻导管吸氧比例、无创机械通气（CPAP）及入住儿童重症监护室（PICU）比例低于<5岁组（P<0.05）。<5岁大叶性肺炎亚组中位年龄、过敏体质比例、热峰≥39.0 ℃比例、肺部呼吸音减弱比例、WBC、MP耐药比例、支气管镜比例、甲泼尼龙治疗比例、住院时间高于<5岁非大叶性肺炎亚组（P<0.05）；≥5岁大叶性肺炎亚组过敏体质比例、热峰≥39 ℃、呼吸音减弱比例、D-二聚体、耐药、支气管镜和甲泼尼龙比例、住院时间高于≥5岁非大叶性肺炎亚组，喘息、三凹征和氧疗比例低于≥5岁非大叶性肺炎亚组（P<0.05）。多因素Logistic逐步回归分析显示，年龄≥5岁、过敏体质、热峰≥39.0 ℃、NLR升高及MP耐药是发生大叶性肺炎的高危因素（P<0.05）。

<5岁年龄组肺部体征更明显，更需氧疗和PICU的支持；而≥5岁组肺外症状更明显，住院时间更长，易进展为大叶性肺炎，且耐药发生率高，需要糖皮质激素和支气管肺泡灌洗治疗更为常见。年龄≥5岁、过敏体质、热峰≥39.0 ℃、NLR升高及耐药是发生大叶性肺炎的高危因素。