Pulmonary mucoepidermoid carcinoma in children: two case reports and a review of the literature.

Pulmonary mucoepidermoid carcinoma (PMEC) is a rare tumor, particularly in children, and its clinical manifestations vary. When the tumor is small, it may be asymptomatic; however, with larger tumors, patients may present with symptoms such as recurring pneumonia, atelectasis, persistent cough, chest pain, and even hemoptysis. PMEC appears as an exophytic intrabronchial mass. This study aims to report on the clinical manifestations, imaging findings, treatment approaches, and prognosis of two children diagnosed with PMEC at our hospital between January 2018 and December 2022. The age of onset for both children was 9 years, and the masses were located in the right upper lobe bronchi. Following surgical treatment, both patients showed a good prognosis. In addition, we conducted a comprehensive review of the relevant literature to enhance the overall understanding of PMEC.

The clinical significance of allergen-specific IgG4 in allergic diseases.

IgG4 is a subclass of IgG antibody with a unique molecular feature of (Fragment antigen- binding) Fab-arm exchange, allowing bispecific antigen binding in a mono-valent manner. With low binding affinity to C1q and Fcγreceptors, IgG4 is incapable of forming immune complexes and activating the complement pathway, exhibiting a non-inflammatory feature. IgG4 is produced similarly to IgE and is considered a modified reaction to IgE class-switching response under certain conditions. It could also counteract IgE-activated inflammation. However, the clinical significance of IgG4 in allergic diseases is complex and controversial. Three viewpoints have been suggested to describe the role of IgG4. IgG4 can act as a tolerance-inducer to play a protective role under repeated and rapid incremental dosing of allergen exposure in allergen immunotherapy (AIT), supported by allergies in cat raisers and venom desensitization in beekeepers. Another viewpoint accepted by mainstream specialists and guidelines of Food Allergy and Management in different countries points out that food-specific IgG4 is a bystander in food allergy and should not be used as a diagnostic tool in clinical work. However, eosinophilic esophagitis (EoE) investigation revealed a direct clinical relevance between physiopathology and serum IgG4 in cow milk and wheat. These factors indicate that allergen-specific IgG4 plays a multifaceted role in allergic diseases that is protective or pathogenic depending on different allergens or exposure conditions.

The clinical application of flexible bronchoscopy in a neonatal intensive care unit.

Objective: Flexible bronchoscopy is widely used in infants and it plays a crucial role. The aim of this study was to investigate the value and clinical safety of flexible bronchoscopy in a neonatal intensive care unit. Methods: A retrospective analysis was performed on the clinical data of 116 neonates who underwent flexible bronchoscopy and the outcomes of 147 procedures. A correlation analysis was performed on the relationship between flexible bronchoscopy findings, microscopic indications, and clinical disease. Results: The 147 procedures performed were due to the following reasons: problems related to artificial airways, 58 cases (39.45%); upper respiratory problems, 60 cases (40.81%) (recurrent dyspnea, 23 cases; upper airway obstruction, 17 cases; recurrent stridor, 14 cases; and hoarseness, six cases), lower respiratory problems, 51 cases (34.69%) (persistent pneumonia, 21 cases; suspicious airway anatomical disease, 21 cases; recurrent atelectasis, eight cases; and pneumorrhagia, one case), feeding difficulty three cases (2.04%). The 147 endoscopic examinations were performed for the following reasons: pathological changes, 141 cases (95.92%); laryngomalacia, 78 cases (53.06%); mucosal inflammation/secretions, 64 cases (43.54%); vocal cord paralysis, 29 cases (19.72%); trachea/bronchus stenosis, 17 cases (11.56%) [five cases of congenital annular constriction of the trachea, seven cases of left main tracheal stenosis, one case of the right middle bronchial stenosis, two cases of tracheal compression, and two cases of congenital tracheal stenosis]; subglottic lesions, 15 cases (10.20%) [eight cases of subglottic granulation tissue, six cases of subglottic stenosis, one cases of subglottic hemangioma]; tracheomalacia, 14 cases (9.52%); laryngeal edema, five cases (3.40%); tracheoesophageal fistula, four cases (2.72%); rhinostenosis, three cases (2.04%); tracheal bronchus, three cases (2.04%); glossoptosis, two cases (1.36%); laryngeal cyst, two cases (1.36%); laryngeal cleft, two cases (1.36%); tongue base cysts, one case (0.68%); and pneumorrhagia, one case (0.68%). Complications were rare and mild. Conclusion: Flexible bronchoscopy is safe and effective for diagnosing and differentiating neonatal respiratory disorders in neonatal intensive care units.

Case Report: Intermittent Chest Pain With Cough, Fever, and Pericardial Effusion Over the Course of 1 Year in an 11-Year-Old Girl.

An 11-year-old girl presented with frequent chest pain, fever, and a cough that she had had for more than 13 months, as well as pleural effusion and large pericardial effusion. She was misdiagnosed with tuberculosis and received anti-tuberculosis drugs for 6 months. Within the past year, she also underwent two more thoracotomies and a thoracoscopic partial pericardiectomy. The final diagnosis of pulmonary paragonimiasis was established once it was known that she had eosinophilia, always drank stream water, and tested positive for antibodies against Paragonimus. Since antiparasitic praziquantel therapy was effective, paragonimiasis should be considered as a possibility in the differential diagnosis of tuberculosis in children.

Evaluation of a Novel Simulation Curriculum With the Segmented Model in Pediatric Cardiovascular Education.

Objective: The need to develop the full range of knowledge, skills, and professionalism poses new challenges for pediatric cardiovascular education. This study aimed to investigate the effectiveness of a novel simulation curriculum with the segmented model for pediatric cardiovascular residents. Materials and Methods: First, the simulation course was designed according to a prior survey and based on a human patient simulator setting. Then, another 55 residents were randomly selected and assigned to participate in a simulation course (about acute fulminant myocarditis in children), either in the experimental group or the control group. Taking full advantage of the simulation education, the simulation case in the experimental group was divided into three segments and included a micro-debriefing at the end of each segment. The three segments were independent but together formed the whole case. It was designed through three cycles of running and debriefing, and more challenging tasks were gradually proposed to residents. The case in the control group was not split and included only one case running and debriefing. The assessments of the residents' knowledge, skills, professionalism performance, and satisfaction feedback from residents were analyzed to evaluate the effectiveness of the course. Results: In total, 44 residents completed the whole experimental period, including 23 participants in the experimental group and 21 participants in the control group. The pre-course knowledge assessment scores of the two groups were comparable, while the mean post-course score in the experimental group was 82.61 ± 17.38, which was significantly higher than that in the control group (50.48 ± 18.57, p < 0.01). The mean skills assessment score of residents in the experimental group was 84.17 ± 6.01, which was significantly higher than the control group (54.50 ± 5.72, p < 0.01). In terms of the professionalism assessment, the residents in the experimental group achieved better performance than those in the control group in all aspects (respect, privacy, communication, responsibility, and cooperation) (p < 0.05). Satisfaction feedback from residents showed that self-confidence regarding knowledge mastery in the experimental group was significantly higher than that in the control group (p < 0.05), while there were no significant differences in the evaluations of the teacher's performance (p > 0.05). Conclusions: The novel simulation curriculum with the segmented model helps residents achieve better performance in terms of knowledge, skills, and professionalism while improving self-confidence. It has some value in pediatric cardiovascular education and is worthy of further promotion.

Clinical Features in Patients with Xq23 Microdeletion: A Case Report and Literature Review

Xq22.3-q23 microdeletion is a rare genomic disorder. The purpose of this study was to emphasize the correlation between clinical phenotype and genotype of proximal deletion on chromosome Xq22.3-q23. A 5 years old boy had a 671 KB microdeletion on Xq23 by chromosomal microarray analysis, including AMMECR1 and CHRDL1 genes. He presented with microsomia, midface hypoplasia, right kidney dysplasia and mildly motor retardation, which have not previously been reported in relation to Xq23 deletion. To the best of our knowledge, this is the first case with Xq23 microdeletion. A total of nine cases with microdeletion at Xq22.3-q23 affecting AMMECR1 and two cases with CHRDL1 mutation were reviewed. This review showed that Xq23 microdeletion with microsomia, midface hypoplasia, kidney dysplasia, and mild motor retardation was rare. The previous literature showed two novel point mutations in AMMECR1 and CHRDL1 with some phenotype difference from the presented case. Xq23 microdeletion should be considered for patients with microsomia, midface hypoplasia, kidney dysplasia and growth retardation.

Pulmonary Nocardia infection in a child with idiopathic pulmonary hemosiderosis.

BACKGROUND: Idiopathic pulmonary hemosiderosis (IPH) encompasses a rare and agnogenic group of diffuse alveolar capillary hemorrhagic diseases. Corticosteroid treatment is the globally preferred therapeutic strategy for IPH; however, it can cause immunodeficiency. Nocardia infection often occurs in immunocompromised patients and primarily involves the pleura and lungs. Herein, we describe a case of pediatric pulmonary Nocardia infection after the corticosteroid treatment of IPH. CASE PRESENTATION: A 7-year-old girl presented with chief complaints of pale complexion persisting for 1 year and a cough for 20 days. Abundant hemosiderin-laden macrophages were detected in the gastric juice, which supported the diagnosis of IPH. Uninterrupted doses of corticosteroids were administered during the last hospitalization. After nearly 2 months of corticosteroids therapy, the patient began to cough and produce a purulent sputum. Next-generation sequencing of the bronchoalveolar lavage fluid revealed Nocardia abscessus (N. abscessus) DNA. Linezolid was administered with good response, and the patient was discharged after 18 days of hospitalization. Her symptoms and pulmonary lesions had recovered, and the IPH appeared to be well-controlled with low dose of corticosteroids in follow-up. CONCLUSIONS: Nocardia infection should be considered in the differential diagnoses for IPH patients receiving corticosteroid therapy, especially in patients with poor response to conventional empirical antibiotic therapy. Next-generation sequencing of bronchoalveolar lavage fluid may be used to quickly identify the Nocardia. Sulfonamides or linezolid are effective for pediatric pulmonary Nocardia infection.

A Novel RFXANK Mutation in a Chinese Child With MHC II Deficiency: Case Report and Literature Review.

Major histocompatibility complex (MHC) II deficiency is a rare primary immunodeficiency disorder that is characterized by the deficiency of MHC class II molecules. The disease is caused by transcription factor mutations including class II transactivator (CIITA), regulatory factor X-5 (RFX5), RFX-associated protein (RFXAP), and RFXAP-containing ankyrin repeat (RFXANK), respectively. Mutations in the RFXANK gene account for >70% of all known patients worldwide. Herein, we reported a 10-month-old boy with MHC II deficiency caused by a novel mutation in the RFXANK gene (c.337 + 1G>C). The boy was admitted to the hospital due to pneumonia and diarrhea at 4 months of age. Genetic analysis revealed a novel homozygous mutation in the RFXANK gene, which derived from the c.337 + 1G>C heterozygous mutations in the RFXANK gene of his parents. The boy died 3 months after diagnosis. More than 200 cases have been reported, and a review of the literature revealed different mutation rates of 4 transcription factors in different countries or regions. This is the first case report of MHC II deficiency from East Asia. We also describe all gene mutations that cause MHC II deficiency and the epidemiology of MHC II deficiency with gene mutations in this paper.

Pulmonary Alveolar Proteinosis Due to Pneumocystis carinii in Type 1 Hyper-IgM Syndrome: A Case Report.

Background: Pulmonary alveolar proteinosis (PAP) is a rare diffuse lung disease. Reports of rare cases of PAP due to Pneumocystis jirovecii (P. jirovecii) exist in infants with immunodeficiency diseases, but no cases have been reported to date in pediatric patients with type 1 hyper-IgM syndrome (HIGM1). Case Presentation: Herein, we present a case of PAP secondary to P. jirovecii on an infant with HIGM1. He was admitted to our unit because of cough and tachypnea. Lung biopsy confirmed the diagnosis of PAP, whereas hexamine-silver staining of the bronchoalveolar lavage fluid identified P. jirovecii infection. No other probable cause of PAP was observed. Whole exome sequencing indicated a novel c.511dupA (p.I171N*30) hemizygous mutation in the CD40 ligand (CD40LG) gene. He was cured with bronchoalveolar lavage and compound sulfamethoxazole tablets. Conclusions: To our knowledge, this is the first reported case of P. jirovecii infection as a reversible cause of PAP in an infant with HIGM1.

Plastic bronchitis due to adenoviral infection: a case report.

BACKGROUND: Plastic bronchitis (PB) frequently occurs as a serious postoperative complication of the Fontan procedure. The definitive causes of PB are unknown. CASE PRESENTATION: Herein, we report a pediatric case of PB secondary to adenoviral infection. A 4-year-old girl was admitted to the general pediatric ward for cough since 2 weeks and fever since 11 days. Consolidated lesions were noted in the right upper and both lower lung lobes. Extracorporeal membrane oxygenation was performed because the patient's respiratory failure remained unalleviated despite the use of a ventilator. Bronchial dendritic casts were extracted using flexible bronchoscopy, and the patient's breathing improved. Pathological examination of the dendritic cast confirmed the diagnosis of type I PB. The exfoliated cells of sputum and cells from bronchoalveolar lavage fluid were positive for adenoviral antigen. Human adenovirus 7 was detected by next-generation sequencing of the bronchoalveolar lavage fluid. The patient recovered and was discharged 39 days after admission without recurrence of cough or wheezing. CONCLUSIONS: PB due to human adenovirus 7 infection should be considered in children with persistent respiratory failure. Flexible bronchoscopy should be performed early to confirm diagnosis and to remove any airway obstruction.

Diagnosis and treatment recommendations for pediatric respiratory infection caused by the 2019 novel coronavirus.

Since December 2019, an epidemic caused by novel coronavirus (2019-nCoV) infection has occurred unexpectedly in China. As of 8 pm, 31 January 2020, more than 20 pediatric cases have been reported in China. Of these cases, ten patients were identified in Zhejiang Province, with an age of onset ranging from 112 days to 17 years. Following the latest National recommendations for diagnosis and treatment of pneumonia caused by 2019-nCoV (the 4th edition) and current status of clinical practice in Zhejiang Province, recommendations for the diagnosis and treatment of respiratory infection caused by 2019-nCoV for children were drafted by the National Clinical Research Center for Child Health, the National Children's Regional Medical Center, Children's Hospital, Zhejiang University School of Medicine to further standardize the protocol for diagnosis and treatment of respiratory infection in children caused by 2019-nCoV.

Sonic hedgehog (Shh) and CC chemokine ligand 2 signaling pathways in asthma.

Asthma is a chronic inflammatory disease of the airways in which many cells are involved, including mast cells, eosinophils, T lymphocytes, and so on. During the process, many chemokines and mediators are released to engage in recruiting and activating eosinophils and other inflammatory cells. Also, some signaling pathways are involved in the pathobiology of asthma. Sonic hedgehog (Shh) is one of the members of hedgehog gene families. Shh signaling plays a critical role in the embryonic development, including the lung. Previous findings from our team reveal that Shh is involved in the asthma pathogenesis. Recombinant Shh could induce the CC chemokine ligand 2 (CCL2) overexpressing and Smo inhibitor GDC-O449 could inhibit CCL2 expression in airway epithelial cells, monocytes, or macrophages. Hence, we reviewed the effects of Shh and CCL2 signaling pathways, and the interaction between signaling pathways in asthma.

In vitro activity and clinical efficacy of macrolides, cefoperazone-sulbactam and piperacillin/piperacillin-tazobactam against Bordetella pertussis and the clinical manifestations in pertussis patients due to these isolates: A single-centre study in Zhejiang Province, China.

BACKGROUND AND OBJECTIVE: Macrolides are the recommended antibiotics for treating pertussis and preventing transmission. The causative bacterium, Bordetella pertussis, has high macrolide resistance and has recently circulated in China. The objective of this study was to find effective alternative antibiotics for treatment by assessing the in vitro activity and clinical efficacy of antibiotics against Bordetella pertussis. METHODS: Bordetella pertussis was confirmed by agglutination with specific antisera and mass spectrometry. The MICs of antibiotics against isolates were determined using the Etest method. Treatment outcomes were clinically and microbiologically evaluated. RESULTS: A total of 126 pertussis patients were diagnosed based on culture, 69.8% of whom were aged ≤6 months and 72.1% were treated with previous macrolides. Leucocytosis and lymphocytosis were observed in 29.4% and 54.8% of all patients, respectively. Both MIC50 and MIC90 of erythromycin, azithromycin, and clindamycin were >256mg/L, and 75.4% were highly macrolide resistant. The MIC90 of trimethoprim-sulfamethoxazole, ampicillin, ampicillin-sulbactam, cefuroxime, ceftriaxone and cefoperazone-sulbactam were 0.38mg/L, 0.25mg/L, 0.19mg/L, 12mg/L, 0.19mg/L and 0.047mg/L, respectively. The MICs of piperacillin in all of the isolations were <0.016mg/L. Of the patients treated with single cefoperazone-sulbactam or piperacillin-tazobactam, 30 of 32 (93.8%) had significantly improved clinical symptoms and 24 of 25 (96%) had negative culture results after 2 weeks of therapy. CONCLUSION: Macrolide resistance in Bordetella pertussis is a serious problem in Zhejiang Province, China. Piperacillin/piperacillin-tazobactam and cefoperazone-sulbactam have potent antibacterial activity in vitro and in vivo, and may become the alternative choice for treating pertussis caused by macrolide-resistant isolates.

The Differential Expression Profiles of miRNA-let 7a, 7b, and 7c in Bronchoalveolar Lavage Fluid From Infants With Asthma and Airway Foreign Bodies.

The aim of this study was to investigate the expression patterns of miRNA-let 7a, 7b, and 7c in bronchoalveolar lavage fluid in infants with asthma and airway foreign bodies. Between January 2016 and February 2017, 27 infants were included and divided into observation group (infants with asthma, n = 15) and control group (infants with airway foreign bodies, n = 12). The differential expression profiles of miRNA-let 7a, 7b, and 7c were determined by reverse transcription-polymerase chain reaction in bronchoalveolar lavage fluid (BALF) from infants of the 2 groups. The BALF was collected from infants undergoing flexible bronchoscopy. MiRNA-let 7a, 7b, and 7c increased significantly in infants from observation group as compared with control group (2.72 ± 0.48 vs 1, 8.23 ± 1.64 vs 1, 3.16 ± 0.62 vs 1, respectively). The increased expression of miRNA-let 7a, 7b, and 7c were associated with the asthma of infants.

Diagnosis and treatment of allergic diseases in Zhejiang Province: a cross-sectional survey.

BACKGROUND: The specialty of allergy developed quickly in western countries because of the rapid increase of allergic diseases, whereas it developed relatively slowly in China. The prevalence of allergen sensitization and allergic diseases in Zhejiang Province of China is high and improving the medical services for these diseases is critically needed. OBJECTIVE: To investigate the working status of the diagnosis and treatment of allergic diseases, including doctor resources, diagnostic methods, and allergen-specific immunotherapy in patients of Zhejiang Province, and to provide instructions for the strategic development of subspecialties of allergic diseases. METHODS: First we defined the doctors who treat allergic diseases, and designed a comprehensive questionnaire to collect personal and hospital information for these doctors. The questionnaires were distributed to hospitals with different ranks and from different areas in the province. The general condition of doctor's resources, carryout of diagnostic methods, and allergen-specific immunotherapy were described and variations in the different specialties, hospitals, and areas were further analyzed. RESULTS: Doctors in their thirties with bachelor's degrees were the mainstream for diagnosing and treating allergic diseases. The main specialties of the doctor resources were the specialties of Ear, Nose and Throat (ENT), Respirology, Pediatrics, and Dermatology. The Pediatrics specialty had a more reasonable infrastructure of doctor resources with more young doctors working in this subspecialty. The development of allergy subspecialty varied within hospitals at different levels or from different areas. The carryout of the skin prick test (SPT), serum specific IgE (ssIgE), and subcutaneous immunotherapy (SCIT) was best performed in provincial hospitals, while sublingual immunotherapy (SLIT) was prescribed most commonly in municipal hospitals. The performance of SPT and ssIgE in Hangzhou, Jiaxing, and Wenzhou areas was much better than that in other places. The performance of SCIT and SLIT was best in Wenzhou. CONCLUSIONS: Our survey revealed a very initial and unbalanced development for the allergy subspecialty in Zhejiang Province. Doctor resources for allergic diseases were mainly from the specialties of ENT, Respirology, and Pediatrics, and the performance of diagnosis and treatment was mainly focused on provincial and municipal hospitals. Continuous education of allergies could be extended to primary healthcare centers and more efforts should be directed to those areas with poor medical resources.

Effect of low birth weight on childhood asthma: a meta-analysis.

BACKGROUND: Low birth weight is strongly correlated with an increased risk of adult diseases. Additionally, low birth weight might be a risk factor for asthma later in life. METHODS: A systematic literature search of the PubMed database from 1966 to November 2013 was conducted. The criteria for inclusion of papers were as follows: case-control or cohort studies; the odds ratio (OR) or risk ratio (RR) estimates with the corresponding 95% confidence intervals (CIs) were presented, or there were sufficient data for calculation; and studies were published in English up to October 2013. Random-effect and fixed-effect meta-analyses, meta-regression, and cumulative meta-analysis were conducted. RESULTS: Thirteen cohort studies and 1,105,703 subjects were included. The overall pooled RRs (95% CIs) of asthma risk for low birth weight were 1.162 (fixed-effects model, 95% CI, 1.128-1.197) and 1.152 (random-effects model, 95% CI, 1.082-1.222). In stratified analyses, the effect of low birth weight on childhood asthma was strong, particularly in studies conducted in Europe, those with a small sample size, and those published recently. A meta-regression analysis did not find significant determinants. CONCLUSIONS: This meta-analysis shows that low birth weight significantly increases the risk of childhood asthma.

Paragonimiasis in chinese children: 58 cases analysis.

OBJECTIVE: To analyze the clinical and radiological features of paragonimiasis in children and raise the awareness of this disease. METHODS: A total of 58 paragonimiasis patients were reviewed. They were 42 boys and 16 girls aged 2.0 to 15.3 years. FINDINGS: Among these patients, 20 were diagnosed in the recent 5 years, 46 with a history of raw water or food ingestion. Except 2 patients without any complaint, the most common features involved the systemic (41, 70.7%) and respiratory systems (43, 74.1%), followed by abdominal, cardiac and nervous systems, with rash and mass. Eosinophilia was noted in 46 (79.3%) patients, granulocytosis in 45 (77.6%), anemia in 14 (24.1%), and thrombocytopenia in 3. Imageology showed pneumonia in 26 (44.8%) patients, pleurisy in 28 (48.3%), hydropericardium in 17 (29.3%), ascites in 16 (27.6%), and celiac lymphadenitis in 13 (22.4%). Besides hepatomegaly and splenomegaly, calcification and multiple lamellar low echogenic areas in the liver were noted, each in one patient. Abnormal brain imaging was noted in 4 of 10 patients. Karyocyte hyperplasia with eosinophilia was noted in all the 19 patients who received bone marrow puncture. CONCLUSION: Paragonimiasis should be considered in the differential diagnosis of patients with multiple organs or system lesions, especially those with eosinophilia, serous cavity effusion, respiratory, cardiac, digestive system, nervous system abnormality, and/or mass. Healthy eating habit is helpful for paragonimiasis prevention.

Epidemiological characteristics and meteorological factors of childhood Mycoplasma pneumoniae pneumonia in Hangzhou.

BACKGROUND: Mycoplasma pneumoniae (M. pneumoniae) is an important pathogen of pediatric respiratory infections and the relation of M. pneumoniae pneumonia (MPP) with meteorological factors remains obscure. This study aims to investigate the epidemiological characteristics of childhood MPP and observe if there is a relationship between epidemiological characteristics and meteorological factors in Hangzhou. METHODS: M. pneumoniae DNA in nasopharyngeal aspirates of hospitalized pneumonia children were detected by polymerase chain reaction from January 1, 2007 to December 31, 2009. The positive rates of MPP (MPP rates) in different years, seasons and ages were compared. The relationship between MPP rates and meteorological data, including mean air temperature (°C), mean relative humidity (%), monthly precipitation (mm) and raining days were analyzed. RESULTS: In 14 799 pneumonia cases found from 2007 to 2009, the MPP rate was 18.5%. Altogether 1610 boys (16.9%) and 1134 girls (21.4%) suffered from MPP with a significant difference between both genders (χ(2)=45.68, P<0.001). In children younger than 1 year, 1-2 years, 3-6 years, and older than 7 years, the MPP rates were 9.8%, 21.1%, 44.4% and 61.6%, respectively. The MPP rates were significantly higher in older children than in younger ones (trends test χ(2)=46.72, P<0.001). In a descending order, the MPP rates in summer, autumn, spring, and winter were 27.8%, 23.9%, 18.0% and 11.6%, respectively (χ(2)=372.75, P<0.001). The MPP rates in 2007 to 2009 were 12.9%, 19.3% and 23.6%, respectively (trends test χ(2)=13.72, P<0.001). Of the four meteorological factors, only monthly mean air temperature was included in the multiple linear regression model (P<0.001). CONCLUSIONS: This study showed that the MPP rate was higher in older children than in younger ones. Girls had a higher positive rate of MPP than boys. In Hangzhou, MPP was more prevalent in summer and autumn. Air temperature was the only meteorological factor affecting the prevalence of MPP.