Biallelic human SHARPIN loss of function induces autoinflammation and immunodeficiency.

The linear ubiquitin assembly complex (LUBAC) consists of HOIP, HOIL-1 and SHARPIN and is essential for proper immune responses. Individuals with HOIP and HOIL-1 deficiencies present with severe immunodeficiency, autoinflammation and glycogen storage disease. In mice, the loss of Sharpin leads to severe dermatitis due to excessive keratinocyte cell death. Here, we report two individuals with SHARPIN deficiency who manifest autoinflammatory symptoms but unexpectedly no dermatological problems. Fibroblasts and B cells from these individuals showed attenuated canonical NF-κB responses and a propensity for cell death mediated by TNF superfamily members. Both SHARPIN-deficient and HOIP-deficient individuals showed a substantial reduction of secondary lymphoid germinal center B cell development. Treatment of one SHARPIN-deficient individual with anti-TNF therapies led to complete clinical and transcriptomic resolution of autoinflammation. These findings underscore the critical function of the LUBAC as a gatekeeper for cell death-mediated immune dysregulation in humans.

Adaptive immune responses to SARS-CoV-2 persist in the pharyngeal lymphoid tissue of children.

Most studies of adaptive immunity to SARS-CoV-2 infection focus on peripheral blood, which may not fully reflect immune responses at the site of infection. Using samples from 110 children undergoing tonsillectomy and adenoidectomy during the COVID-19 pandemic, we identified 24 samples with evidence of previous SARS-CoV-2 infection, including neutralizing antibodies in serum and SARS-CoV-2-specific germinal center and memory B cells in the tonsils and adenoids. Single-cell B cell receptor (BCR) sequencing indicated virus-specific BCRs were class-switched and somatically hypermutated, with overlapping clones in the two tissues. Expanded T cell clonotypes were found in tonsils, adenoids and blood post-COVID-19, some with CDR3 sequences identical to previously reported SARS-CoV-2-reactive T cell receptors (TCRs). Pharyngeal tissues from COVID-19-convalescent children showed persistent expansion of germinal center and antiviral lymphocyte populations associated with interferon (IFN)-γ-type responses, particularly in the adenoids, and viral RNA in both tissues. Our results provide evidence for persistent tissue-specific immunity to SARS-CoV-2 in the upper respiratory tract of children after infection.

Protein phosphatase 2A propels follicular T helper cell development in lupus.

Follicular helper T (Tfh) cells are important for generating humoral immune responses by helping B cells form germinal centers (GCs) and the production of high-affinity antibodies. However, aberrant Tfh cell expansion also contributes to the generation of self-reactive autoantibodies and promotes autoantibody-mediated autoimmune diseases such as systemic lupus erythematosus (SLE). Protein phosphatase 2A catalytic subunit alpha isoform (PP2A Cα) expression levels are elevated in peripheral T cells of SLE patients and positively correlate with autoantibody titers and disease activity. Here, we demonstrate a critical role of PP2A in Tfh differentiation by using T cell restricted PP2A Cα deficient mice. We observed impaired Tfh differentiation and GC response in two different classical Tfh induction models. Mechanistic studies revealed that downregulation of protein translation of the Tfh lineage transcription factor BCL6 in PP2A deficient T cells. Importantly, we found that PP2A deficiency by either gene knockout or chemical inhibition alleviated lupus severity in mice. Lastly, we confirmed a positive correlation between PP2A Cα and BCL6 protein levels in human CD4+ T cells from patients with SLE. In summary, our study revealed a critical role of PP2A in regulating Tfh cells and suggests it is a potential therapeutic target for lupus.

Common genetic susceptibility loci link PFAPA syndrome, Behçet's disease, and recurrent aphthous stomatitis.

Periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome is the most common periodic fever syndrome in children. The disease appears to cluster in families, but the pathogenesis is unknown. We queried two European-American cohorts and one Turkish cohort (total n = 231) of individuals with PFAPA for common variants previously associated with two other oropharyngeal ulcerative disorders, Behçet's disease and recurrent aphthous stomatitis. In a metaanalysis, we found that a variant upstream of IL12A (rs17753641) is strongly associated with PFAPA (OR 2.13, P = 6 × 10-9). We demonstrated that monocytes from individuals who are heterozygous or homozygous for this risk allele produce significantly higher levels of IL-12p70 upon IFN-γ and LPS stimulation than those from individuals without the risk allele. We also found that variants near STAT4, IL10, and CCR1-CCR3 were significant susceptibility loci for PFAPA, suggesting that the pathogenesis of PFAPA involves abnormal antigen-presenting cell function and T cell activity and polarization, thereby implicating both innate and adaptive immune responses at the oropharyngeal mucosa. Our results illustrate genetic similarities among recurrent aphthous stomatitis, PFAPA, and Behçet's disease, placing these disorders on a common spectrum, with recurrent aphthous stomatitis on the mild end, Behçet's disease on the severe end, and PFAPA intermediate. We propose naming these disorders Behçet's spectrum disorders to highlight their relationship. HLA alleles may be factors that influence phenotypes along this spectrum as we found new class I and II HLA associations for PFAPA distinct from Behçet's disease and recurrent aphthous stomatitis.

Ultrasound of the vocal cords in infants.

Vocal cord paralysis is a common cause of respiratory and feeding problems in the pediatric population. While the causes of vocal cord paralysis are multiple, iatrogenic injury of the recurrent laryngeal nerve after cardiovascular surgery is the most frequent cause. Vocal cord paralysis increases the risk of swallowing dysfunction, tracheal aspiration and pneumonia. It also increases the need for nasoenteric feeds and gastrostomy tube placement. Flexible nasopharyngolaryngoscopy is considered the gold standard for diagnosing vocal cord paralysis, but it has significant drawbacks: it is uncomfortable, it can trigger a cardiovascular event in children with unstable cardiovascular status, it can be challenging to perform, and it can be difficult to interpret. Laryngeal US has become a popular imaging modality to evaluate the function of the vocal cords. Laryngeal US is well-tolerated, easy to perform, simple to interpret and has a lower physiological impact compared to flexible nasopharyngolaryngoscopy. Laryngeal US is an accurate and low-cost diagnostic test for vocal cord paralysis. In this review, we describe the anatomy of the larynx and recurrent laryngeal nerve; the causes, symptoms and pathophysiology of vocal cord paralysis; laryngeal US technique; diagnostic criteria for vocal cord paralysis; and a reporting system.

The financial impact of clinic no-show rates in an academic pediatric otolaryngology practice.

PURPOSE: To investigate determinants of no-show rates in an academic pediatric otolaryngology practice including appointment time, age, sex, new patient status, payer mix, and median household income by zip code. MATERIALS AND METHODS: Retrospective chart review of clinic no-show rates and patient demographics in a free standing children's hospital and affiliated outpatient clinics across eight providers in a one-year period. RESULTS: Analysis shows that the overall no-show rate across all providers was 15% with the highest rate of 19% in the zip code with the lowest median income. Highest no-shows are in June, but overall, seasons did not play a significant role in no-show rates. Male gender, morning appointments, and having public insurance appear to significantly predict no-shows. Lost revenue on no-shows range from $191K to $384K per year. The average percentage of the amount billed paid by insurance range from the lowest by out-of-state Medicaid at 16% to the highest by managed care at 54%. CONCLUSIONS: No-show rates account for a significant portion of lost revenue in the outpatient setting for an academic practice, and can be predicted by lower median income, male gender, morning appointments, and public insurance. Such patients may need different appointment reminders. Future clinic templates should be optimized for no-shows to increase productivity and access to care.

Total colonic aganglionosis and imperforate anus in a severely affected infant with Pallister-Hall syndrome.

Pallister-Hall syndrome is a complex malformation syndrome characterized by a wide range of anomalies including hypothalamic hamartoma, polydactyly, bifid epiglottis, and genitourinary abnormalities. It is usually caused by truncating frameshift/nonsense and splicing mutations in the middle third of GLI3. The clinical course ranges from mild to lethal in the neonatal period. We present the first patient with Pallister-Hall syndrome reported with total colonic aganglionosis, a rare form of Hirschsprung disease with poor long-term outcome. The patient also had an imperforate anus, which is the third individual with Pallister-Hall syndrome reported with both Hirschsprung disease and an imperforate anus. Molecular testing via amniocentesis showed an apparently de novo novel nonsense mutation c.2641 C>T (p.Gln881*). His overall medical course was difficult and was complicated by respiratory failure and pan-hypopituitarism. Invasive care was ultimately withdrawn, and the patient expired at three months of age. This patient's phenotype was complex with unusual gastrointestinal features ultimately leading to a unfavorable prognosis and outcome, highlighting the range of clinical severity in patients with Pallister-Hall syndrome.

Total Airway Reconstruction in the Neonate: Combined Mandibular Distraction and Slide Tracheoplasty for Multiple Level Airway Obstruction.

BACKGROUND: Long-segment congenital tracheal stenosis (CTS) is characterized by segmental tracheal stenosis, complete tracheal rings, and absent posterior pars membranosa for >50% of tracheal length. Slide tracheoplasty on cardiopulmonary bypass (CPB) has traditionally been the procedure of choice for airway reconstruction. Pierre Robin sequence (PRS) is characterized by the triad of micrognathia, glossoptosis, and airway obstruction. The authors and others, have demonstrated the efficacy of mandibular distraction osteogenesis (MDO) to avoid tracheostomy in severe cases of PRS. METHODS: The authors present a unique case of the multidisciplinary management of long-segment CTS and concomitant PRS via total airway reconstruction off CPB, involving our otolaryngology, cardiothoracic, and plastic surgery teams. RESULTS: This 36-week baby girl, prenatally diagnosed with PRS and polyhydramnios concerning for airway obstruction, was delivered via planned ex utero intrapartum treatment (EXIT). Tracheostomy was aborted because of long-segment CTS. A 2.5-French endotracheal tube (ETT) was temporarily sutured in before transfer to our facility for definitive airway management.Bilateral MDO was performed without complication at 2 weeks old (distraction to 20mm by postoperative day 25). At 6 weeks old, delayed slide tracheoplasty avoiding cardiopulmonary bypass was followed by an uneventful recovery. Most recent follow-up demonstrates airway patency without signs of obstruction. CONCLUSIONS: This patient's case is the first reporting combined MDO and slide tracheoplasty to relieve multilevel neonatal airway obstruction. Unique and challenging, it demonstrates the importance of multidisciplinary management of complex neonatal airway obstruction.

Exploring Mental Health in a Pediatric Paradoxical Vocal Fold Motion Sample Using Patient-Reported Outcomes.

OBJECTIVE: Paradoxical vocal fold motion (PVFM) is characterized by inappropriate adduction of vocal folds during inspiration causing dyspnea. While anxiety is suspected to be a predisposing factor, incidence has been understudied. STUDY DESIGNS: Retrospective review. SETTING: Multidisciplinary PVFM hospital clinic. METHODS: We used patient-reported outcome measures to examine anxiety and depression in consecutive patients aged 10 to 17 years using Pediatric SFv1.1 Anxiety 8b and Level 2-Depression inventories (parents completed proxy forms). T-scores were classified as normal (none to slight <55) or elevated (mild 55-59.9, moderate 60-69.9, severe >70). RESULTS: Twenty-three pediatric patients and 20 parents completed surveys. Mean age was 13.74 years. For anxiety, 69.6% of patients and 40% of parents identified elevated levels. For depression, 30.4% of patients and 15% of parents identified elevated levels. Therapy need for the sample was 65.2% (34.8% active in services and 30.4% referred). Child anxiety scores were significantly higher in the therapy need group, U = 17, P = .004. CONCLUSION: This study of adolescents with PVFM confirmed elevated anxiety and depression scores in 2/3 of the participants. Anxiety likely precedes diagnosis and is a predisposing factor. Referral for individualized intervention targeting anxiety and depression is indicated.

Spatial Morphoproteomic Features Predict Uniqueness of Immune Microarchitectures and Responses in Lymphoid Follicles.

Multiplex imaging technologies allow the characterization of single cells in their cellular environments. Understanding the organization of single cells within their microenvironment and quantifying disease-status related biomarkers is essential for multiplex datasets. Here we proposed SNOWFLAKE, a graph neural network framework pipeline for the prediction of disease-status from combined multiplex cell expression and morphology in human B-cell follicles. We applied SNOWFLAKE to a multiplex dataset related to COVID-19 infection in humans and showed better predictive power of the SNOWFLAKE pipeline compared to other machine learning and deep learning methods. Moreover, we combined morphological features inside graph edge features to utilize attribution methods for extracting disease-relevant motifs from single-cell spatial graphs. The underlying subgraphs were further analyzed and associated with disease status across the dataset. We showed that SNOWFLAKE successfully extracted significant low dimensional embedding from subgraphs with a clear separation between disease status and helped characterize unique cellular interactions in the subgraphs. SNOWFLAKE is a generalizable pipeline for the analysis of multiplex imaging data modality by extracting disease-relevant subgraphs guided by graph-level prediction.

Characterization and treatment of patients with chronic rhinosinusitis and nasal polyps.

BACKGROUND: Patients with chronic rhinosinusitis (CRS) and nasal polyps (NPs) may be subdivided into aspirin-sensitive (AS) and aspirin-tolerant (AT) populations. These cohorts are not well characterized. OBJECTIVE: To examine phenotypic characteristics and determine the extent of medical/surgical interventions in patients with CRS+NP and to compare the AS with the AT subset in the CRS+NP sample. METHODS: Retrospective chart review was performed at a tertiary academic respiratory hospital. Data included patient demographics, asthma severity, peripheral eosinophilia, Lund-Mackay computed tomographic score, symptomatic dysosmia, and therapeutic interventions. RESULTS: Of the 182 patients included, 81 had aspirin sensitivity (45%) and 101 had aspirin tolerance (55%). Asthma was present in 94% of patients with CRS+NP (100% in AS subgroup vs 89% in AT subgroup, P = .001). Eighty-eight percent of the CRS+NP sample had moderate to severe persistent asthma. In the AS and AT subgroups, asthma severity was similar (P > .6). The CRS+NP sample showed a mean computed tomographic score of 14.0 (44% with eosinophilia and 46% with dysosmia). More severe sinus disease was noted in the AS group (Lund-Mackay computed tomographic scores, P = .002; olfactory symptoms, P = .001). Serum eosinophil levels were not statistically different between groups (51% in AS group, 39% in AT group, P > .1). CONCLUSION: This study is one of the broadest reviews of patients with CRS+NP, with unique findings in the high prevalence of asthma in AS and AT patients, greater olfactory dysfunction in AS patients, and a minority of patients with CRS+NP and circulating eosinophils. Most AS patients do not have increased circulating eosinophils, as is often believed. These results shed further light on the association between asthma and upper respiratory tract disease in those with nasal polyposis.

Managing the Destructive Foreign Body: Water Beads in the Ear (A Case Series) and Literature Review.

OBJECTIVE: To characterize our experience with super-absorbent polymer beads placed in the external auditory canal to better understand the damage caused and subsequent management required. METHODS: Retrospective chart review of pediatric patients at 2 separate tertiary referral centers. RESULTS: Seven patients were identified as having placed super-absorbent polymer beads in the external auditory canal, 6 of whom required removal under general anesthesia. Three patients did not suffer otologic trauma or hearing loss (average foreign body duration <72 hours). Four patients experienced severe otologic complications (average foreign body duration >1 week), all of whom were treated with otologic drops prior to bead identification. Of this severe complication group, 3 patients had restored hearing after surgical intervention, while 1 patient suffered profound hearing loss secondary to labyrinthitis ossificans. CONCLUSION: Early recognition of otologic foreign bodies is important, particularly if expansile water-bead is suspected. Depending on timeframe, water beads are highly destructive to the middle ear structures, and most patients will require surgical intervention.

Association of anosmia and neutralizing antibody production in adolescents with SARS-CoV-2.

BACKGROUND: To monitor olfactory/gustatory dysfunction and its relationship to SARS-CoV-2 IgG antibody responses in an adolescent population. METHODS: Adolescents with changes in olfactory/gustatory functions were enrolled in a 15-month study. The patients were evaluated with 1) SNOT-22, 2) pediatric smell wheel, and 3) SARS-CoV-2 antibody testing. The relationship between these scores and length of anosmia, and the amount of SARS-CoV-2 IgG antibodies were assessed. A brain MRI was performed in cases of persistent special sensory symptoms. RESULTS: Eighteen patients were identified with smell and/or taste complaints. Most of the patients were female (67%) and median age was 15 years (range 11-17). Twelve patients had prior SARS-CoV-2 PCR testing, with only five patients with a positive result. The median SNOT-22 score was 16 (range 0-52) and the median smell wheel score was 6.5 (range 1-11). Patients with taste difficulty were more likely to have a score less than eight. 78% of the patients tested positive for antibodies and there was a strong negative correlation between smell wheel score and antibody level (Spearman, ρ = -0.798, p = 0.002). Five patients underwent MRI scan, and all resulted as normal olfactory bulb structures. 66% received nasal corticosteroids. 11 patients presented in follow up. CONCLUSIONS: Adolescents presenting to a pediatric ENT clinic during the SARS-CoV-2 pandemic were likely to have prolonged (>6 weeks) symptoms of SARS-CoV-2. The majority do not report positive PCR testing result but do report systemic symptoms including anosmia. This suggests that anosmia may be both a late and prolonged symptom of SARS-CoV-2.

Examining the pediatric subglottic airway by ultrasound: A systematic review.

OBJECTIVE: The purpose of this review was to determine the ability of ultrasound (US) to assess the subglottic airway in pediatric patients to estimate the appropriate size of endotracheal tube (ETT). DATA SOURCES: Pubmed, Scopus, and Embase databases. METHODS: A search of the literature was performed for studies that utilized ultrasonography to examine the minimal transverse diameter of the subglottic airway (MTDSA) in the pediatric (age < 18) population to estimate endotracheal tube (ETT) size. Articles were excluded if they involved adults or non-humans, had no comparison method, or were case reports. The primary outcome was the successful use of ultrasound compared to the reference standard defined by the study. RESULTS: Sixteen studies were included, for a total of 1,633 pediatric subjects in whom transcervical laryngeal ultrasound was used prospectively to examine the MTDSA to estimate ETT size prior to intubation. Ultrasound reliably predicted the clinically best fit endotracheal tube by air leak test in 48-100% of subjects, while age-based formulas were accurate 24-95% of the time. Ultrasound was highly predictive of proper size, with R2 ranging between 0.684 to 0.980. Of those reintubated (n = 104), 86 (83%) required larger-sized tubes, while 18 (17%) required smaller-sized tubes. Both methods tended to underestimate ETT size, but the age-based formulas accounted for most of these differences. CONCLUSION: Transcervical laryngeal ultrasound appears to be a reliable predictor of endotracheal tube size in children undergoing elective surgery, which has implications for preventing intubation-related trauma and ensuring adequate ventilation for those who may require prolonged intubation.

Multi-Institutional Study of Patient-Reported Outcomes of Paradoxical Vocal Fold Motion.

OBJECTIVE: To explore patient-reported outcome measures of pediatric paradoxical vocal fold motion through a multi-institutional study of geographically diverse United States medical facilities to assess long-term management and outcomes. METHODS: Eligible participants >8 years of age diagnosed with PVFM over a 10-year period from 7 tertiary pediatric hospitals were invited to complete a survey addressing study objectives. RESULTS: 65 participants completed the survey, of whom 80% were female, 75% reported a 3.5 grade point average or better, and 75% identified as competitive athletes or extremely athletic individuals. Participants rated their perceived efficacy of 13 specific treatments. Only five treatments were considered effective by a majority of the participants who tried them. The treatments that participants tried most often were breathing exercises (89.2%), bronchodilator treatments (45%), and allergy medications (35.4%). 78.8% of participants reported receiving more than one treatment and 25% reported receiving a combination of bronchodilators, anticholinergics, and steroids. At the time of PVFM diagnosis, 38% of participants had no idea when their symptoms would completely resolve. 23.3% of participants did not experience symptom resolution until greater than 1 year after diagnosis. CONCLUSIONS: Traditional management tools such as breathing exercises and biofeedback treatments may not provide the long-term benefit that providers anticipate. In addition to these commonly used management strategies, highly efficacious techniques such as counseling and lifestyle management should be incorporated into the long-term management of patients whose symptoms are refractory to traditional care. LEVEL OF EVIDENCE: 4 Laryngoscope, 133:970-976, 2023.

Examining multi-level immune response to determine prevalence of COVID-19 in pediatric tonsillectomy.

OBJECTIVE: To determine the prevalence of COVID-19 in a cohort of children undergoing tonsillectomy through assessment of B cell immune responses to SARS-CoV-2 in both peripheral blood and tonsil tissue. METHODS: In this cohort study at a tertiary pediatric hospital (Children's National Hospital) in Washington, DC, we recruited 100 children undergoing tonsillectomy from late September 2020 to January 2021. Serum, peripheral blood cells, and tonsil tissue were collected and examined for immune reactivity to SARS-CoV-2. Parent-reported clinical histories were compared to antibody and B-cell responses. RESULTS: Among 100 children undergoing tonsillectomy, 19% had evidence of immune responses to SARS-CoV-2 (CoV2+), indicating prior COVID-19. In all seropositive participants, we detected SARS-CoV-2 specific B cells in both peripheral blood mononuclear cells and tonsils, providing evidence for tissue-specific immunity in these children. Of the 19, 63% reported no known history of COVID-19, and an additional 3 were asymptomatic or unaware of an acute infection when detected on pre-surgery screen. Hispanic children represented 74% of CoV2+ subjects compared to 37% of the full cohort. 100% of CoV2+ children lived in a zip code with poverty level >10%. CONCLUSIONS: Nearly one-fifth of children undergoing tonsillectomy at an urban U.S. hospital had evidence of prior COVID-19 during the early pandemic, with the majority unaware of prior infection. Our results underscore the ethnic and socio-economic disparities of COVID-19. We found concordant evidence of humoral immune responses in children in both blood and tonsil tissue, providing evidence of local immune responses in the upper respiratory tract. LEVEL OF EVIDENCE: 3 Laryngoscope, 133:1993-1999, 2023.

Ectopic pituitary adenoma of the clivus presenting with apoplexy: case report and review of the literature.

Ectopic pituitary adenomas usually occur within sphenoid sinus or nasopharynx, and seldom within the clivus. There is only a single reported example of ectopic adenoma with clinical apoplexy, albeit not from clivus. We report a 78-year-old male with known prostate carcinoma admitted with acute onset of blurred vision, suggestive of apoplexy. Work-up revealed unilateral cranial nerve VI palsy and neuroimaging showed a mass confined to the clivus; sellar region was normal. Preoperative considerations included chordoma, chondrosarcoma, or metastatic prostate carcinoma to bone. Resection was via endoscopic transsphenoidal approach to the clivus. An ectopic null cell pituitary adenoma with bland infarction was identified as the cause of the patient's clinical apoplexy. No antecedent precipitating factors for apoplexy were present; specifically the patient had not received leuprolide preoperatively, a known precipitant of pituitary apoplexy in prostate cancer patients who receive drug. We review the literature on ectopic clival pituitary adenomas, apoplexy in ectopic adenomas, and the link between apoplexy and leuprolide usage.

Robust, persistent adaptive immune responses to SARS-CoV-2 in the oropharyngeal lymphoid tissue of children.

SARS-CoV-2 infection triggers adaptive immune responses from both T and B cells. However, most studies focus on peripheral blood, which may not fully reflect immune responses in lymphoid tissues at the site of infection. To evaluate both local and systemic adaptive immune responses to SARS-CoV-2, we collected peripheral blood, tonsils, and adenoids from 110 children undergoing tonsillectomy/adenoidectomy during the COVID-19 pandemic and found 24 with evidence of prior SARS-CoV-2 infection, including detectable neutralizing antibodies against multiple viral variants. We identified SARS-CoV-2-specific germinal center (GC) and memory B cells; single cell BCR sequencing showed that these virus-specific B cells were class-switched and somatically hypermutated, with overlapping clones in the adenoids and tonsils. Oropharyngeal tissues from COVID-19-convalescent children showed persistent expansion of GC and anti-viral lymphocyte populations associated with an IFN-γ-type response, with particularly prominent changes in the adenoids, as well as evidence of persistent viral RNA in both tonsil and adenoid tissues of many participants. Our results show robust, tissue-specific adaptive immune responses to SARS-CoV-2 in the upper respiratory tract of children weeks to months after acute infection, providing evidence of persistent localized immunity to this respiratory virus.

Variations in expression of matrix metalloproteinase-9 and tissue inhibitor of metalloproteinase-1 in nasal mucosa of aspirin-sensitive versus aspirin-tolerant patients with nasal polyposis.

BACKGROUND: Matrix metalloproteinases (MMPs) are key enzymes responsible for extracellular matrix degradation contributing to the progressive histological changes seen in lower airway disease, including asthma. MMP-9 and TIMP-1 have also shown some role in the pathogenesis of chronic rhinosinusitis (CRS) and nasal polyposis (NP). OBJECTIVE: We aim to determine variability in expression of MMP-9 and its inhibitor, tissue inhibitor of metalloproteinase-1 (TIMP-1), in sinus tissue from distinct patient populations presenting with nasal polyposis. METHODS: The expression of MMP-9 and TIMP-1 was investigated in nasal polyp tissue from 6 aspirin-sensitive (AS) and 6 aspirin-tolerant (AT) patients undergoing endoscopic sinus surgery for chronic rhinosinusitis with nasal polyposis (CRSwNP). Sinus mucosa from 6 patients with chronic rhinosinusitis without nasal polyposis (CRSsNP) was used as control. The MMP-9 and TIMP-1 expression was measured using immunofluorescence technique and graded using manual and computerized methods. RESULTS: Expression of TIMP-1 was significantly reduced in the AS group when compared with both the AT and CRSsNP (control) groups (P < .001). The MMP-9/TIMP-1 ratio was significantly increased in the AS group when compared with other patient groups (P < .001). The MMP- 9 expression was similar between study and control groups. CONCLUSION: These results support the importance of MMP-9 and TIMP-1 expression in nasal polyp formation. The decreased expression of TIMP-1 in AS patients may promote the effects of MMP-9 expression and thus contribute to tissue remodeling and inflammatory changes. This finding may lead to further understanding of disease severity and resistance to treatment in this group of patients, as well as the pathogenesis of nasal polyps.