FUT2 Variants Confer Susceptibility to Familial Otitis Media.

Non-secretor status due to homozygosity for the common FUT2 variant c.461G>A (p.Trp154∗) is associated with either risk for autoimmune diseases or protection against viral diarrhea and HIV. We determined the role of FUT2 in otitis media susceptibility by obtaining DNA samples from 609 multi-ethnic families and simplex case subjects with otitis media. Exome and Sanger sequencing, linkage analysis, and Fisher exact and transmission disequilibrium tests (TDT) were performed. The common FUT2 c.604C>T (p.Arg202∗) variant co-segregates with otitis media in a Filipino pedigree (LOD = 4.0). Additionally, a rare variant, c.412C>T (p.Arg138Cys), is associated with recurrent/chronic otitis media in European-American children (p = 1.2 × 10-5) and US trios (TDT p = 0.01). The c.461G>A (p.Trp154∗) variant was also over-transmitted in US trios (TDT p = 0.01) and was associated with shifts in middle ear microbiota composition (PERMANOVA p < 10-7) and increased biodiversity. When all missense and nonsense variants identified in multi-ethnic US trios with CADD > 20 were combined, FUT2 variants were over-transmitted in trios (TDT p = 0.001). Fut2 is transiently upregulated in mouse middle ear after inoculation with non-typeable Haemophilus influenzae. Four FUT2 variants-namely p.Ala104Val, p.Arg138Cys, p.Trp154∗, and p.Arg202∗-reduced A antigen in mutant-transfected COS-7 cells, while the nonsense variants also reduced FUT2 protein levels. Common and rare FUT2 variants confer susceptibility to otitis media, likely by modifying the middle ear microbiome through regulation of A antigen levels in epithelial cells. Our families demonstrate marked intra-familial genetic heterogeneity, suggesting that multiple combinations of common and rare variants plus environmental factors influence the individual otitis media phenotype as a complex trait.

A2ML1 and otitis media: novel variants, differential expression, and relevant pathways.

A genetic basis for otitis media is established, however, the role of rare variants in disease etiology is largely unknown. Previously a duplication variant within A2ML1 was identified as a significant risk factor for otitis media in an indigenous Filipino population and in US children. In this report exome and Sanger sequencing was performed using DNA samples from the indigenous Filipino population, Filipino cochlear implantees, US probands, Finnish, and Pakistani families with otitis media. Sixteen novel, damaging A2ML1 variants identified in otitis media patients were rare or low-frequency in population-matched controls. In the indigenous population, both gingivitis and A2ML1 variants including the known duplication variant and the novel splice variant c.4061 + 1 G>C were independently associated with otitis media. Sequencing of salivary RNA samples from indigenous Filipinos demonstrated lower A2ML1 expression according to the carriage of A2ML1 variants. Sequencing of additional salivary RNA samples from US patients with otitis media revealed differentially expressed genes that are highly correlated with A2ML1 expression levels. In particular, RND3 is upregulated in both A2ML1 variant carriers and high-A2ML1 expressors. These findings support a role for A2ML1 in keratinocyte differentiation within the middle ear as part of otitis media pathology and the potential application of ROCK inhibition in otitis media.

Obstructive Sleep Apnea and Sleep Position: Does It Matter for Infants With a Cleft Palate?

OBJECTIVE: To determine whether nonsupine sleep improves obstructive sleep apnea (OSA) in infants with cleft palate undergoing polysomnography (PSG). DESIGN: Retrospective chart review. SETTING: Tertiary care pediatric hospital. PATIENTS: Twenty-seven infants (1 month to 1 year) with cleft palate with or without cleft lip (CP ± L) undergoing PSG testing for suspected OSA were included. MAIN OUTCOME MEASURES: Polysomnography measures included obstructive apnea-hypopnea index (OAHI), central apnea-hypopnea index (CAHI), oxygen saturation (SpO2) nadir, SpO2, and end-tidal carbon dioxide (ETCO2). RESULTS: Twenty-three PSGs with at least 20 minutes of sleep in both the supine and the nonsupine positions were analyzed. The supine OAHI (mean: 16.8 events/hour; standard deviation [SD]: 18.5) and nonsupine OAHI (mean: 12.6 events/hour; SD: 12.6) did not differ significantly (P = .10). The supine CAHI (mean: 1.9 events/hour; SD: 2.7) and nonsupine CAHI (mean: 3.1 events/hour; SD: 3.7; P = .15), the supine SpO2 nadir (mean: 81.2%; SD: 6.3) and nonsupine SpO2 nadir (mean: 81.8%; SD: 5.3; P = .70), the supine mean SpO2 (mean: 95.5%; SD: 1.9) and nonsupine mean SpO2 saturation (mean: 95.3%; SD: 2.4; P = .34), and the supine ETCO2 (mean: 45.4 mm Hg; SD: 5.3) and nonsupine ETCO2 (mean: 42.5 mm Hg; SD: 10.1; P = .24) were also similar. CONCLUSIONS: There were no significant improvements in OSA metrics during nonsupine sleep in infants with CP ± L. Prior to recommending nonsupine positioning which increases infant's exposure to sudden infant death syndrome risk, we advocate obtaining a PSG to verify an objective improvement in OSA.

Women Surgeons Who Contributed to the Development of Pediatric Otolaryngology in the United States.

OBJECTIVE: Our goal was to identify the early pioneering women surgeons in the United States who devoted their career or the majority of their practice to the care of otolaryngologic disorders in children. We sought to share their stories, recognize their contributions to the surgical subspecialty now known as pediatric otolaryngology, and acknowledge their vision and leadership. DATA SOURCES: Primary sources include books, published articles in the medical literature, newspaper articles, memorials/obituaries in both the medical literature and lay press, web logs, the John Q Adams Center for the History of Otolaryngology to include the Women in Otolaryngology, a number of otolaryngology departments, and children's hospitals nationwide. Interviews were conducted with former colleagues and senior pediatric otolaryngologists. REVIEW METHODS: Following review of all available information, women surgeons were included in this study if there was documentation of a clinical practice involving the otolaryngologic care of children in the United States before 1985 with demonstration of the education of others in this discipline. RESULTS: Six women surgeons were identified: Drs. Alice G Bryant, Margaret F. Butler, Ellen James Patterson, Emily Lois Van Loon, LaVonne Bernadene Bergstrom, and Joyce A. Schild. CONCLUSION: Six pioneering women surgeons in the United States have been identified who devoted their practice to the care of otolaryngologic disorders in children and mentored or trained other health care providers. The stories of their lives, their contributions to the care of otolaryngologic disorders in children, and their work as mentors or educators have been described. Laryngoscope, 134:40-46, 2024.

Otitis Media in Children with Down Syndrome Is Associated with Shifts in the Nasopharyngeal and Middle Ear Microbiotas.

Background: Otitis media (OM) is defined as middle ear (ME) inflammation that is usually due to infection. Globally, OM is a leading cause of hearing loss and is the most frequently diagnosed disease in young children. For OM, pediatric patients with Down syndrome (DS) demonstrate higher incidence rates, greater severity, and poorer outcomes. However, to date, no studies have investigated the bacterial profiles of children with DS and OM. Method: We aimed to determine if there are differences in composition of bacterial profiles or the relative abundance of individual taxa within the ME and nasopharyngeal (NP) microbiotas of pediatric OM patients with DS (n = 11) compared with those without DS (n = 84). We sequenced the 16S rRNA genes and analyzed the sequence data for diversity indices and relative abundance of individual taxa. Results: Individuals with DS demonstrated increased biodiversity in their ME and NP microbiotas. In children with OM, DS was associated with increased biodiversity and higher relative abundance of specific taxa in the ME. Conclusion: Our findings suggest that dysbioses in the NP of DS children contributes to their increased susceptibility to OM compared with controls. These findings suggest that DS influences regulation of the mucosal microbiota and contributes to OM pathology.

Rare Coding Variants in Patients with Non-Syndromic Vestibular Dysfunction.

Vertigo due to vestibular dysfunction is rare in children. The elucidation of its etiology will improve clinical management and the quality of life of patients. Genes for vestibular dysfunction were previously identified in patients with both hearing loss and vertigo. This study aimed to identify rare, coding variants in children with peripheral vertigo but no hearing loss, and in patients with potentially overlapping phenotypes, namely, Meniere's disease or idiopathic scoliosis. Rare variants were selected from the exome sequence data of 5 American children with vertigo, 226 Spanish patients with Meniere's disease, and 38 European-American probands with scoliosis. In children with vertigo, 17 variants were found in 15 genes involved in migraine, musculoskeletal phenotypes, and vestibular development. Three genes, OTOP1, HMX3, and LAMA2, have knockout mouse models for vestibular dysfunction. Moreover, HMX3 and LAMA2 were expressed in human vestibular tissues. Rare variants within ECM1, OTOP1, and OTOP2 were each identified in three adult patients with Meniere's disease. Additionally, an OTOP1 variant was identified in 11 adolescents with lateral semicircular canal asymmetry, 10 of whom have scoliosis. We hypothesize that peripheral vestibular dysfunction in children may be due to multiple rare variants within genes that are involved in the inner ear structure, migraine, and musculoskeletal disease.

Novel candidate genes for cholesteatoma in chronic otitis media.

Cholesteatoma is a rare and benign disease, but its propensity to cause erosive damage through uninhibited growth can be detrimental to hearing and health. Prior reports indicated a genetic component to pathogenesis in at least a subset of patients. In this study, we aimed to identify rare DNA variants in affected patients. The salivary DNA of six patients whose middle ear tissues were obtained during tympanoplasty/mastoidectomy surgeries were submitted for exome sequencing. Tissue samples from the same patients were previously submitted for mRNA sequencing and analyzed for differentially expressed genes (DEGs). From the generated exome sequence data, rare predicted-to-be-damaging variants were selected within previously identified DEGs, and the candidate genes within which these rare variants lie were used for network analysis. Exome sequencing of six DNA samples yielded 5,078 rare variants with minor allele frequency <.001. A total of 510 variants were predicted to be deleterious and 52 were found to lie within previously identified DEGs. After selecting variants based on quality control measures, 12 variants were identified all from one pediatric patient. Network analysis identified ten significant cellular pathways, including protein transport, viral process, regulation of catalytic activity and cell cycle, and apoptotic and rhythmic processes. We hypothesize that the candidate genes identified in this study may be part of key signaling pathways during the mucosal response to middle ear infection. The occurrence of multiple rare variants may play a role in earlier onset of cholesteatoma formation in chronic otitis media.

The FUT2 Variant c.461G>A (p.Trp154*) Is Associated With Differentially Expressed Genes and Nasopharyngeal Microbiota Shifts in Patients With Otitis Media.

Otitis media (OM) is a leading cause of childhood hearing loss. Variants in FUT2, which encodes alpha-(1,2)-fucosyltransferase, were identified to increase susceptibility to OM, potentially through shifts in the middle ear (ME) or nasopharyngeal (NP) microbiotas as mediated by transcriptional changes. Greater knowledge of differences in relative abundance of otopathogens in carriers of pathogenic variants can help determine risk for OM in patients. In order to determine the downstream effects of FUT2 variation, we examined gene expression in relation to carriage of a common pathogenic FUT2 c.461G>A (p.Trp154*) variant using RNA-sequence data from saliva samples from 28 patients with OM. Differential gene expression was also examined in bulk mRNA and single-cell RNA-sequence data from wildtype mouse ME mucosa after inoculation with non-typeable Haemophilus influenzae (NTHi). In addition, microbiotas were profiled from ME and NP samples of 65 OM patients using 16S rRNA gene sequencing. In human carriers of the FUT2 variant, FN1, KMT2D, MUC16 and NBPF20 were downregulated while MTAP was upregulated. Post-infectious expression in the mouse ME recapitulated these transcriptional differences, with the exception of Fn1 upregulation after NTHi-inoculation. In the NP, Candidate Division TM7 was associated with wildtype genotype (FDR-adj-p=0.009). Overall, the FUT2 c.461G>A variant was associated with transcriptional changes in processes related to response to infection and with increased load of potential otopathogens in the ME and decreased commensals in the NP. These findings provide increased understanding of how FUT2 variants influence gene transcription and the mucosal microbiota, and thus contribute to the pathology of OM.

The role of CDHR3 in susceptibility to otitis media.

Otitis media (OM) is common in young children and can cause hearing loss and speech, language, and developmental delays. OM has high heritability; however, little is known about OM-related molecular and genetic processes. CDHR3 was previously identified as a locus for OM susceptibility, but to date, studies have focused on how the CDHR3 p.Cys529Tyr variant increases epithelial binding of rhinovirus-C and risk for lung or sinus pathology. In order to further delineate a role for CDHR3 in OM, we performed the following: exome sequencing using DNA samples from OM-affected individuals from 257 multi-ethnic families; Sanger sequencing, logistic regression and transmission disequilibrium tests for 407 US trios or probands with OM; 16S rRNA sequencing and analysis for middle ear and nasopharyngeal samples; and single-cell RNA sequencing and differential expression analyses for mouse middle ear. From exome sequence data, we identified a novel pathogenic CDHR3 splice variant that co-segregates with OM in US and Finnish families. Additionally, a frameshift and six missense rare or low-frequency variants were identified in Finnish probands. In US probands, the CDHR3 p.Cys529Tyr variant was associated with the absence of middle ear fluid at surgery and also with increased relative abundance of Lysobacter in the nasopharynx and Streptomyces in the middle ear. Consistent with published data on airway epithelial cells and our RNA-sequence data from human middle ear tissues, Cdhr3 expression is restricted to ciliated epithelial cells of the middle ear and is downregulated after acute OM. Overall, these findings suggest a critical role for CDHR3 in OM susceptibility. KEY MESSAGES: • Novel rare or low-frequency CDHR3 variants putatively confer risk for otitis media. • Pathogenic variant CDHR3 c.1653 + 3G > A was found in nine families with otitis media. • CDHR3 p.Cys529Tyr was associated with lack of effusion and bacterial otopathogens. • Cdhr3 expression was limited to ciliated epithelial cells in mouse middle ear. • Cdhr3 was downregulated 3 h after infection of mouse middle ear.

Multi-omic studies on missense PLG variants in families with otitis media.

Otitis media (OM), a very common disease in young children, can result in hearing loss. In order to potentially replicate previously reported associations between OM and PLG, exome and Sanger sequencing, RNA-sequencing of saliva and middle ear samples, 16S rRNA sequencing, molecular modeling, and statistical analyses including transmission disequilibrium tests (TDT) were performed in a multi-ethnic cohort of 718 families and simplex cases with OM. We identified four rare PLG variants c.112A > G (p.Lys38Glu), c.782G > A (p.Arg261His), c.1481C > T (p.Ala494Val) and c.2045 T > A (p.Ile682Asn), and one common variant c.1414G > A (p.Asp472Asn). However TDT analyses for these PLG variants did not demonstrate association with OM in 314 families. Additionally PLG expression is very low or absent in normal or diseased middle ear in mouse and human, and salivary expression and microbial α-diversity were non-significant in c.1414G > A (p.Asp472Asn) carriers. Based on molecular modeling, the novel rare variants particularly c.782G > A (p.Arg261His) and c.2045 T > A (p.Ile682Asn) were predicted to affect protein structure. Exploration of other potential disease mechanisms will help elucidate how PLG contributes to OM susceptibility in humans. Our results underline the importance of following up findings from genome-wide association through replication studies, preferably using multi-omic datasets.

Identification of Novel Genes and Biological Pathways That Overlap in Infectious and Nonallergic Diseases of the Upper and Lower Airways Using Network Analyses.

Previous genetic studies on susceptibility to otitis media and airway infections have focused on immune pathways acting within the local mucosal epithelium, and outside of allergic rhinitis and asthma, limited studies exist on the overlaps at the gene, pathway or network level between the upper and lower airways. In this report, we compared [1] pathways identified from network analysis using genes derived from published genome-wide family-based and association studies for otitis media, sinusitis, and lung phenotypes, to [2] pathways identified using differentially expressed genes from RNA-sequence data from lower airway, sinus, and middle ear tissues, in particular cholesteatoma tissue compared to middle ear mucosa. For otitis media, a large number of genes (n = 1,806) were identified as differentially expressed between cholesteatoma and middle ear mucosa, which in turn led to the identification of 68 pathways that are enriched in cholesteatoma. Two differentially expressed genes CR1 and SAA1 overlap in middle ear, sinus, and lower airway samples and are potentially novel genes for otitis media susceptibility. In addition, 56 genes were differentially expressed in both tissues from the middle ear and either sinus or lower airways. Pathways that are common in upper and lower airway diseases, whether from published DNA studies or from our RNA-sequencing analyses, include chromatin organization/remodeling, endocytosis, immune system process, protein folding, and viral process. Taken together, our findings from genetic susceptibility and differential tissue expression studies support the hypothesis that the unified airway theory wherein the upper and lower respiratory tracts act as an integrated unit also applies to infectious and nonallergic airway epithelial disease. Our results may be used as reference for identification of genes or pathways that are relevant to upper and lower airways, whether common across sites, or unique to each disease.

Multiple surgeries in pediatric otolaryngology patients and associated anesthesia risks.

OBJECTIVES: To determine the risk of healthy children undergoing tympanostomy tubes of an additional surgery prior to age three and associated risk factors. METHODS: A retrospective chart review of pediatric patients at a tertiary metropolitan children's hospital who underwent tympanostomy tube insertion procedure before age of three from January 2010 through March 2015. We determined patient demographics, indication for tympanostomy tube insertion, as well as information about additional procedures requiring general anesthesia before the age of three years. A prospective telephone interview was also performed on a portion of the study population to assess if there were additional surgeries before the age of three that did not occur at our institution. RESULTS: In our institution there was a 13% risk of getting an additional surgery after tympanostomy tubes in children who are otherwise healthy. The most common second procedure was an otolaryngologic procedure in 77.8% of the cases. Children with a diagnosis of recurrent acute otitis media had a threefold greater chance of getting an additional surgery than those with a diagnosis of chronic otitis media with effusion. Patients that identified as Black or African American were 3.2 times more likely to have additional surgery. With every year increase at age of surgery, the odds of an additional surgery decreased by 77%. CONCLUSIONS: In healthy children undergoing tympanostomy tube insertion at our institution, the incidence of additional procedures under general anesthesia (GA) is low at 13%. Although there is evidence of possible deleterious effects of anesthesia on the developing brain, it is generally accepted that one short (≤1 h) anesthetic exposure under the age of three has not been associated with adverse neurodevelopmental outcomes. As a specialty that regularly performs procedures on young children, we need to be aware of the possible effects of anesthetic agents on our patients. However, this study shows that the exposure risk is low and should help reassure patient's families.

Microtia and congenital aural atresia.

Microtia and congenital aural atresia (CAA) are congenital anomalies that are so common that every otolaryngologist should be familiar with the initial evaluation and care of the patient. When one ear hears normally, speech and language development should be normal. The gross and fine motor development of the baby or child is not expected to be affected in isolated cases of microtia and CAA. Current technologies allow for reconstruction or habilitation of the microtic ear when the child is several years of age. The hope is that tissue engineering can eliminate donor site morbidity. Temporary prosthetic ears will remain an option. Aural atresia work continues to be very dependent on the patient anatomy and the need or desire for better hearing in the affected ear.

Presentation and management of nasal foreign bodies at a tertiary children's hospital in an American metro area.

OBJECTIVES: To examine rates of otolaryngology intervention in children presenting to our emergency department with nasal foreign bodies, factors associated with otolaryngology involvement, rates of complications, and details on nasal button battery exposure. METHODS: All patients presenting with a nasal foreign body to Children's Hospital Colorado from 2007 to 2012 were identified. Factors leading to referral to otolaryngology and operative intervention were examined, as well as complications. RESULTS: 102 patients were included. 36 (35%) patients were referred to the otolaryngology clinic, of which 58.9% required operating room intervention. 66 (64.7%) children had their nasal foreign bodies removed in the emergency room, however 30 (45%) of these were removed by an otolaryngology resident or attending physician. Overall, 64.7% of nasal foreign bodies required removal by otolaryngology. Of the 15 objects removed in the operating room, six were button batteries. No septal perforations occurred as a result of nasal button battery exposure. Multivariable logistic regression showed two significant predictors of OR removal: age and disc shaped objects. CONCLUSION: While emergency department providers are comfortable attempting removal of nasal foreign bodies, there was a high rate of otolaryngology intervention. Based on this data, there is a need to educate emergency room providers on nasal anatomy and techniques for nasal foreign body removal.

Cricopharyngeal achalasia in children: botulinum toxin injection as a tool for diagnosis and treatment.

OBJECTIVES/HYPOTHESIS: Characteristics and outcomes of pediatric patients undergoing cricopharyngeus injection with botulinum toxin for the treatment of cricopharyngeal achalasia were reviewed. A parental telephone survey was performed to assess improvement and satisfaction. STUDY DESIGN: Retrospective review of patients who underwent injection of the cricopharyngeus with botulinum toxin for cricopharyngeal achalasia. A prospective survey of postoperative symptoms and parental satisfaction was also performed. METHODS: After institutional review board approval, children with cricopharyngeal achalasia who underwent injection with botulinum toxin were identified. Specific parameters were recorded for each patient. A survey of the parents' satisfaction and subjective improvement was then conducted. RESULTS: Six children were identified with cricopharyngeal achalasia, with an age range of 3 months to 10 years. Symptoms varied and five of the six children required some form of altered nutrition. Preoperative studies varied, and the number of injections ranged from one to three per patient. One child had transient worsening of aspiration. Two children benefited from injections and went on to myotomy, while four children did not require myotomy and their symptoms were treated with injections alone. A parental survey was performed via telephone. All parents were satisfied with the procedure. Three children were symptom-free, and three children still exhibit some dysphagia. CONCLUSIONS: Botulinum toxin injection is a useful tool to help diagnose and treat pediatric cricopharyngeal achalasia. More research is needed to elucidate optimal dosing, frequency of injections, and when to move on to surgical intervention. LEVEL OF EVIDENCE: 4.

The internet, adolescent males, and homemade blowgun darts: a recipe for foreign body aspiration.

We describe our experience with blowgun dart aspiration via an illustrative case series and review the resources available to teach children how to construct these objects. A 15-year-old boy presented with cough, wheeze, and eventually admitted to aspiration of a homemade blowgun dart. This instance heightened the awareness of our experience with blowgun dart aspiration as 3 cases presented within a 3-month period. Patients uniformly presented with cough and reported aspiration, and wheezing was noted in 2 of the 3. Although all ultimately admitted their behavior, 2 were initially reluctant to admit aspirating the blowgun dart. Radiographic findings of a needle-shaped metallic airway foreign body were consistent in all patients. Each admitted to finding instructions for blowgun dart construction on the Internet. Emergent rigid bronchoscopy with blowgun dart removal resulted in symptom resolution in all without complication. This represents the largest series of blowgun dart aspiration to date. During deep inhalation, when preparing to propel a blowgun dart, the vocal folds maximally abduct, leading to increased risk for aspiration. Twenty websites were identified providing instructions for the construction of homemade blowgun darts. With the accessibility of the Internet and number of instructional websites, this clinical entity may become more common in the future. Unfortunately, only a few of the websites provide any safety warnings. Certainly, prompt treatment can result in good outcomes; however, serious potential complications, including death, could occur especially given the hesitance our patients showed in divulging the truth of the inciting event.

Complement activation in pediatric patients with recurrent acute otitis media.

OBJECTIVE: Otitis media (OM) is one of the most common childhood diseases. The relative contribution of complement activation in protection and pathogenesis during OM remains largely unknown. The purpose of this study was to investigate the beneficial and pathogenic contributions of complement activation in the middle ear of pediatric patients with recurrent acute otitis media (rAOM), and therefore to provide a rational approach to prevent sequelae of OM such as hearing loss. METHODS: Twenty children undergoing pressure equalization tube placement with or without adenoidectomy for rAOM were enrolled in the study. Bacterial cultures, enzyme-linked immunosorbent assay (ELISA) for complement components and cytokines and western blot for complement activation were performed on middle ear effusion (MEE) and serum samples. The levels of complement C3a, C5a and sC5-b9 in MEEs and serum samples were compared. The levels of these factors were also examined in regards to length of episode. Pearson's correlation coefficients were calculated on variables between C5a and IL-6 or IL-8. Complement gene expression in human middle ear epithelial (HMEE) cells induced by otopathogens was evaluated. Data were analyzed with Student's t test or the Mann-Whitney rank sum test. In all cases, a P value of <0.05 was set as the measure of significance. RESULTS: Our data demonstrated that the complement classical/lectin, alternative and terminal pathways were activated in the middle ear of children with rAOM. Increased complement components of C3a, C5a and sC5-b9 in MEEs were detected in patients with the episode lasting more than six weeks. There was a strong correlation between C5a and IL-6 or IL-8 in the MEEs. Additionally, otopathogens induced enhanced gene expression of factor B and C3 in HMEE cells, which is beneficial for host defense against invading pathogens. CONCLUSION: Our studies provided important new insights on how complement activation contributes to inflammatory process during rAOM. Knowledge of the activity of the complement pathway in patients with rAOM may stimulate the development of new strategies to prevent middle ear inflammatory tissue destruction by directing treatment to specific pathways within the complement cascade.