A genetically modulated Toll-like-receptor-tolerant phenotype in peripheral blood cells of children with multisystem inflammatory syndrome.

Dysregulated innate immune responses contribute to multisystem inflammatory syndrome in children (MIS-C), characterized by gastrointestinal, mucocutaneous, and/or cardiovascular injury occurring weeks after SARS-CoV-2 exposure. To investigate innate immune functions in MIS-C, we stimulated ex vivo peripheral blood cells from MIS-C patients with agonists of Toll-like receptors (TLR), key innate immune response initiators. We found severely dampened cytokine responses and elevated gene expression of negative regulators of TLR signaling. Increased plasma levels of zonulin, a gut leakage marker, were also detected. These effects were also observed in children enrolled months after MIS-C recovery. Moreover, cells from MIS-C children carrying rare genetic variants of lysosomal trafficking regulator (LYST) were less refractory to TLR stimulation and exhibited lysosomal and mitochondrial abnormalities with altered energy metabolism. Our results strongly suggest that MIS-C hyperinflammation and/or excessive or prolonged stimulation with gut-originated TLR ligands drive immune cells to a lasting refractory state. TLR hyporesponsiveness is likely beneficial, as suggested by excess lymphopenia among rare LYST variant carriers. Our findings point to cellular mechanisms underlying TLR hyporesponsiveness; identify genetic determinants that may explain the MIS-C clinical spectrum; suggest potential associations between innate refractory states and long COVID; and highlight the need to monitor long-term consequences of MIS-C.

Characteristics of pediatric COVID-19 infections and the impact of influenza and COVID-19 vaccinations during the first two years of the pandemic.

The data regarding the demographics of SARS-CoV-2 in the pediatric population has been published based on several single-center experiences or on metanalyses over short time frames. This article reports data on the demographics of pediatric patients with COVID-19 on a global scale using the TriNetX COVID-19 Research Network. In addition, we examined the risk of COVID-19 infection in relation to the body mass index (BMI) category and the protective value of influenza and COVID-19 immunization against COVID-19 infection. The incidence of COVID-19 infection was higher in the younger age group (≤6 years old), but no gender differences. The incidence of COVID-19 infection was higher among African Americans/Black race (28.57%) White race (27.10%), and obese patients; across all age groups, all genders, all races, and ethnicities (p < 0.0001). The incidence of MIS-C was also higher in patients with obesity (OR 1.71, CI 1.36-2.14). We found that the patients who were neither vaccinated for COVID-19 nor influenza within one year before their COVID-19 diagnoses compared to those who received influenza vaccine only, had significantly higher odds for hospitalization (OR 1.19, CI 1.18-1.21), development of MIS-C (OR 1.52, CI 1.32-1.74), and more importantly mortality (OR 1.47, CI 1.26-1.71). In addition, those patients who were neither vaccinated for COVID-19 nor influenza within one year before their COVID-19 diagnoses, compared to those who received at least one dose of COVID-19 vaccine, had significantly higher odds for hospitalization (OR 1.11, CI 1.04-1.19). However, those patients who did not receive the influenza vaccine within one year before their COVID-19 diagnoses nor received the COVID-19 vaccine had much higher odds for hospitalization (OR 1.46, CI 1.41-1.51), MIS-C (OR 3.72, CI 2.11-6.56), and mortality compared to those who received both vaccinations (OR 13.55, CI 1.91-9.62). Using the multiplicative interaction scale, we found a positive interaction between the COVID-19 vaccine and the influenza vaccine; they both combined have a larger effect than each separately. Our study is the largest of its kind (to date) examining the global demographic of the pandemic and the first of a kind to find a link between influenza vaccine and COVID-19-related hospitalization, MIS-C, and mortality in the pediatric population.

Researching COVID to enhance recovery (RECOVER) pediatric study protocol: Rationale, objectives and design.

Importance: The prevalence, pathophysiology, and long-term outcomes of COVID-19 (post-acute sequelae of SARS-CoV-2 [PASC] or "Long COVID") in children and young adults remain unknown. Studies must address the urgent need to define PASC, its mechanisms, and potential treatment targets in children and young adults. Observations: We describe the protocol for the Pediatric Observational Cohort Study of the NIH's RE searching COV ID to E nhance R ecovery (RECOVER) Initiative. RECOVER-Pediatrics is an observational meta-cohort study of caregiver-child pairs (birth through 17 years) and young adults (18 through 25 years), recruited from more than 100 sites across the US. This report focuses on two of five cohorts that comprise RECOVER-Pediatrics: 1) a de novo RECOVER prospective cohort of children and young adults with and without previous or current infection; and 2) an extant cohort derived from the Adolescent Brain Cognitive Development (ABCD) study ( n =10,000). The de novo cohort incorporates three tiers of data collection: 1) remote baseline assessments (Tier 1, n=6000); 2) longitudinal follow-up for up to 4 years (Tier 2, n=6000); and 3) a subset of participants, primarily the most severely affected by PASC, who will undergo deep phenotyping to explore PASC pathophysiology (Tier 3, n=600). Youth enrolled in the ABCD study participate in Tier 1. The pediatric protocol was developed as a collaborative partnership of investigators, patients, researchers, clinicians, community partners, and federal partners, intentionally promoting inclusivity and diversity. The protocol is adaptive to facilitate responses to emerging science. Conclusions and Relevance: RECOVER-Pediatrics seeks to characterize the clinical course, underlying mechanisms, and long-term effects of PASC from birth through 25 years old. RECOVER-Pediatrics is designed to elucidate the epidemiology, four-year clinical course, and sociodemographic correlates of pediatric PASC. The data and biosamples will allow examination of mechanistic hypotheses and biomarkers, thus providing insights into potential therapeutic interventions. Clinical Trialsgov Identifier: Clinical Trial Registration: http://www.clinicaltrials.gov . Unique identifier: NCT05172011.

Comprehensive and reliable sonographic assessment and scoring system for inflammatory lesions of the paediatric ankle.

OBJECTIVE: The clinical decision-making process in paediatric arthritis lacks an objective, reliable bedside imaging tool. The aim of this study was to develop a US scanning protocol and assess the reliability of B-mode and Doppler scoring systems for inflammatory lesions of the paediatric ankle. METHODS: As part of the Childhood Arthritis and Rheumatology Research Alliance (CARRA) US group, 19 paediatric rheumatologists through a comprehensive literature review developed a set of standardized views and scoring systems to assess inflammatory lesions of the synovial recesses as well as tendons of the paediatric ankle. Three rounds of scoring of still images were followed by one practical exercise. Agreement among raters was assessed using two-way single score intraclass correlation coefficients (ICC). RESULTS: Of the 37 initially identified views to assess the presence of ankle synovitis and tenosynovitis, nine views were chosen for each B-mode and Doppler mode semi-quantitative evaluation. Several scoring exercises and iterative modifications resulted in a final highly reliable scoring system: anterior tibiotalar joint ICC: 0.93 (95% CI 0.92, 0.94), talonavicular joint ICC: 0.86 (95% CI 0.81, 0.90), subtalar joint ICC: 0.91 (95% CI 0.88, 0.93) and tendons ICC: 0.96 (95% CI 0.95, 0.97). CONCLUSION: A comprehensive and reliable paediatric ankle US scanning protocol and scoring system for the assessment of synovitis and tenosynovitis were successfully developed. Further validation of this scoring system may allow its use as an outcome measure for both clinical and research applications.

Management of Enthesitis in Patients With Psoriatic Arthritis: An Updated Literature Review Informing the 2021 GRAPPA Treatment Recommendations.

OBJECTIVE: Enthesitis is a key pathological and clinical feature of psoriatic arthritis (PsA) in children and adults. Enthesitis is typically assessed clinically using several validated enthesitis scoring systems that have been used in clinical trials. Enthesitis treatment response has been reported as change in the total enthesitis score or the proportion of patients who achieved complete resolution. The majority of trials in PsA did not require patients to have enthesitis at study entry since enthesitis was evaluated only as a secondary outcome. Despite the inherent limitations of the clinical assessment of enthesitis, imaging of the entheses using ultrasound or magnetic resonance imaging has rarely been used in clinical trials to assess response to treatment of enthesitis. This systematic review summarizes existing evidence regarding pharmaceutical and nonpharmaceutical interventions for enthesitis in patients with PsA to facilitate an evidence-based update of the Group for Research and Assessment in Psoriasis and Psoriatic Arthritis (GRAPPA) treatment recommendations for PsA. METHODS: We performed a systematic literature review to identify 41 randomized clinical trials that reported enthesitis treatment response in patients with PsA. For each intervention, the response effect size was summarized and the quality of evidence was graded. Recommendations were then formulated for the various pharmacological and nonpharmacological therapies. RESULTS: We included 41 randomized clinical trials in our review and graded each intervention. CONCLUSION: Several classes of systemic conventional and advanced therapies and local measures were recommended for active enthesitis in patients with PsA.

Reliability of the Pediatric Specific Musculoskeletal Ultrasound Scoring Systems for the Elbow, Wrist, and Finger Joints.

OBJECTIVE: Musculoskeletal ultrasound (MSUS) is increasingly being used in the evaluation of pediatric musculoskeletal diseases. In order to provide objective assessments of arthritis, reliable MSUS scoring systems are needed. Recently, joint-specific scoring systems for arthritis of the pediatric elbow, wrist, and finger joints were proposed by the Childhood Arthritis and Rheumatology Research Alliance (CARRA) MSUS workgroup. This study aimed to assess the reliability of these scoring systems when used by sonographers with different levels of expertise. METHODS: Members of the CARRA MSUS workgroup attended training sessions for scoring the elbow, wrist, and finger. Subsequently, scoring exercises of B mode and power Doppler (PD) mode still images for each joint were performed. Interreader reliability was determined using 2-way single-score intraclass correlation coefficients (ICCs) for synovitis and Cohen [Formula: see text] for tenosynovitis. RESULTS: Seventeen pediatric rheumatologists with different levels of MSUS expertise (1-15 yrs) completed a 2-hour training session and calibration exercise for each joint. Excellent reliability (ICC > 0.75) was found after the first scoring exercise for all the finger and elbow views evaluated on B mode and PD mode, and for all of the wrist views on B mode. After a second training session and a scoring exercise, the wrist PD mode views reached excellent reliability as well. CONCLUSION: The preliminary CARRA MSUS scoring systems for assessing arthritis of the pediatric elbow, wrist, and finger joints demonstrate excellent reliability among pediatric MSUS sonographers with different levels of expertise. With further validation, this reliable joint-specific scoring system could serve as a clinical tool and scientific outcome measure.

Anakinra treatment in multisystemic inflammatory syndrome in children (MIS-C) associated with COVID-19.

Objective: The study aimed to report the efficacy and safety of anakinra treatment in patients with the refractory multisystemic inflammatory syndrome in children (MIS-C). Methods: This is a cross-sectional retrospective study consisting of pediatric patients diagnosed with MIS-C who were treated with anakinra. Results: Among the 378 patients diagnosed with MIS-C, 82 patients (21.6%) who were treated with anakinra were included in the study. The median age of patients was 115 (6-214) months. The median duration of hospitalization was 15 (6-42) days. Sixty patients (73.1%) were admitted to the pediatric intensive care unit. Patients were treated with a median dose of 2.7 mg/kg/day anakinra concomitant with IVIG and steroids. Intravenous anakinra was applied to 12 patients while 70 patients received it subcutaneously. Twenty-eight patients required high dose (4-10 mg/kg/day) anakinra. The median day of anakinra initiation was 2 (1-14) days and the median duration of anakinra use was 7 (1-41) days. No injection site reactions were observed while elevated transaminase levels were detected in 13 patients. Seventy-three patients (89.1%) were discharged without any sequela or morbidity. Seven patients (1.8%) died. Abnormal echocardiographic findings continued in two patients (2.4%) (coronary artery dilatation in one, low ejection fraction in one) at discharge and became normal on the 2nd month. Conclusion: Based on the results of the study, anakinra was associated with clinical improvements and was safe for most patients with refractory MIS-C.

Current Understanding of Multisystem Inflammatory Syndrome (MIS-C) Following COVID-19 and Its Distinction from Kawasaki Disease.

PURPOSE OF REVIEW: In this article, I have reviewed current reports that explore differences and similarities between multisystem inflammatory syndrome in children (MIS-C) and other known multisystem inflammatory diseases seen in children, particularly Kawasaki disease. RECENT FINDINGS: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a human coronavirus causing the COVID-19 disease which emerged in China in December 2019 and spread rapidly to the entire country and quickly to other countries. Currently, there is a pandemic of SARS-CoV-2 infection that results in 20% of patients admitted to hospital with illness, with 3% developing intractable acute respiratory distress syndrome (ARDS) with high mortality. However, pediatric COVID-19 is still reported to be a mild disease, affecting only 8% of children. Pathogenesis in children is comparable to adults. There are suggested impaired activation of IFN-alpha and IFN regulator 3, decreased cell response causing impaired viral defense, yet the clinical course is mild, and almost all children recover from the infection without major complications. Interestingly, there is a subset of patients that develop a late but marked immunogenic response to COVID-19 and develop MIS-C. Clinical features of MIS-C resemble certain pediatric rheumatologic diseases, such as Kawasaki disease (mucocutaneous lymph node syndrome) which affects small-medium vessels. Other features of MIS-C resemble those of macrophage activation syndrome (MAS). However, recent research suggests distinct clinical and laboratory differences between MIS-C, Kawasaki disease, and MAS. Since the start of the SARS-CoV-2 pandemic, MIS-C has become the candidate for the most common cause of acquired heart disease in children.

Leucocytoclastic vasculitis secondary to COVID-19 infection in a young child.

The current case report describes a 13-year-old young boy who presented with purpuric rashes following a completely asymptomatic COVID-19 infection and biopsy-confirmed leucocytoclastic vasculitis, mild haematuria and mild elevation of serum IgA. This case highlights one of the dermatological manifestations of COVID-19 infection which has not been reported so far. Paediatricians should explore the history of this infection when evaluating any child presenting with a vasculitic rash.

Intrarenal injection of mesenchymal stem cell for treatment of lupus nephritis in mice - a pilot study.

The current project is to explore feasibility of direct intra-renal injection of human bone marrow derived mesenchymal stem cells (hMSC) for treatment of lupus nephritis in mice. The treatment protocol involved aged male BXSB (20 weeks) injected with 1 × 106 hMSC unilaterally under the renal capsule. Mice were harvested after 10 weeks follow-up for postmortem exam. Controls included untreated age matched male BXSB and healthy C57Bl/6. At the end of follow-up period, the survival of treated BXSB was 10 folds higher at 62.5% compared to survival of untreated control at 6.3%. The survival of C57Bl/6 remained at 100% with or without similar treatment. The renal pathology review was most significant for decreased tissue inflammation in treated BXSB compared to untreated controls. Renal tissue expression of IL-1b, IL17 were decreased and CTLA-4 was increased by RT PCR among treated compared to untreated BXSB. Thus, direct delivery of hMSC by intrarenal injection is a promising route for treatment of lupus nephritis as shown in this xenogeneic model. Further studies -using expanded numbers of mice to include other lupus strains- are warranted to investigate the mechanisms involved and to optimize treatment protocol for safety and efficacy.

Juvenile Dermatomyositis (JDM) Complicated by Thrombotic Thrombocytopenic Purpura (TTP) and Purtscher's Retinopathy Responsive to Rituximab: Case Report and Literature Review.

Juvenile dermatomyositis (JDM) is a multisystem vasculopathy that infrequently presents with acute complications (1). We report here the case of a 12-year-old girl with JDM who developed Thrombotic Thrombocytopenic purpura (TTP) and Purtscher's retinopathy. This is the second pediatric case of JDM with TTP and Purtscher's retinopathy in the literature. The diagnosis of JDM was based on her clinical presentation (fever, myalgia, proximal muscle weakness, characteristic skin rash and elevated muscle enzymes) (2). Despite improvement of rash, fever and weakness with corticosteroids and intravenous Immunoglobulins (IVIG), the patient developed retinopathy, thrombocytopenia, hemolytic anemia, renal failure, and pulmonary edema within 1 week of initial treatment. A clinical diagnosis of TTP and Purtscher's retinopathy was made and her ADAMTS13 activity was found to be low. Regardless of aggressive treatment with pulse steroid therapy, IVIG, plasmapheresis along with multiple infusions of Fresh Frozen plasma (FFP), her condition deteriorated. In view of her worsening condition, she received one dose of Rituximab and within 48 h, her hematological and retinal involvements improved. Rituximab was given at the same dose once weekly thereafter for 4 total doses. Her disease process was halted, and retinopathy improved significantly in 48 h and continued to gradually improve over 3 weeks of maintenance therapy with cyclosporine, methotrexate, and IVIG and then stabilized. This report documents the association of TTP and Purtscher's retinopathy with JDM, emphasizing that early recognition and prompt treatment with rituximab along with the current standard of care treatment i.e., Vincristine, corticosteroids and plasmapheresis could be of potential benefit in controlling disease activity.

Multisystem Inflammatory Syndrome in U.S. Children and Adolescents.

BACKGROUND: Understanding the epidemiology and clinical course of multisystem inflammatory syndrome in children (MIS-C) and its temporal association with coronavirus disease 2019 (Covid-19) is important, given the clinical and public health implications of the syndrome. METHODS: We conducted targeted surveillance for MIS-C from March 15 to May 20, 2020, in pediatric health centers across the United States. The case definition included six criteria: serious illness leading to hospitalization, an age of less than 21 years, fever that lasted for at least 24 hours, laboratory evidence of inflammation, multisystem organ involvement, and evidence of infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) based on reverse-transcriptase polymerase chain reaction (RT-PCR), antibody testing, or exposure to persons with Covid-19 in the past month. Clinicians abstracted the data onto standardized forms. RESULTS: We report on 186 patients with MIS-C in 26 states. The median age was 8.3 years, 115 patients (62%) were male, 135 (73%) had previously been healthy, 131 (70%) were positive for SARS-CoV-2 by RT-PCR or antibody testing, and 164 (88%) were hospitalized after April 16, 2020. Organ-system involvement included the gastrointestinal system in 171 patients (92%), cardiovascular in 149 (80%), hematologic in 142 (76%), mucocutaneous in 137 (74%), and respiratory in 131 (70%). The median duration of hospitalization was 7 days (interquartile range, 4 to 10); 148 patients (80%) received intensive care, 37 (20%) received mechanical ventilation, 90 (48%) received vasoactive support, and 4 (2%) died. Coronary-artery aneurysms (z scores ≥2.5) were documented in 15 patients (8%), and Kawasaki's disease-like features were documented in 74 (40%). Most patients (171 [92%]) had elevations in at least four biomarkers indicating inflammation. The use of immunomodulating therapies was common: intravenous immune globulin was used in 144 (77%), glucocorticoids in 91 (49%), and interleukin-6 or 1RA inhibitors in 38 (20%). CONCLUSIONS: Multisystem inflammatory syndrome in children associated with SARS-CoV-2 led to serious and life-threatening illness in previously healthy children and adolescents. (Funded by the Centers for Disease Control and Prevention.).

Novel Ultrasound Image Acquisition Protocol and Scoring System for the Pediatric Knee.

OBJECTIVE: The use of musculoskeletal ultrasound is increasing among pediatric rheumatologists. Reliable scoring systems are needed for the objective assessment of synovitis. The aims of this study were to create a standardized and reproducible image acquisition protocol for B-mode and Doppler ultrasound of the pediatric knee, and to develop a standardized scoring system and determine its reliability for pediatric knee synovitis. METHODS: Six pediatric rheumatologists developed a set of standard views for knee assessment in children with juvenile arthritis. Subsequently, a comprehensive literature review, practical exercises, and a consensus process were performed. A scoring system for both B-mode and Doppler was then developed and assessed for reliability. Interreader reliability or agreement among a total of 16 raters was determined using 2-way single-score intraclass correlation coefficient (ICC) analysis. RESULTS: Twenty-one views to assess knee arthritis were initially identified. Following completion of practical exercises and subsequent consensus processes, 3 views in both B-mode and Doppler were selected: suprapatellar longitudinal and medial/lateral parapatellar transverse views. Several rounds of scoring and modifications resulted in a final ICC of suprapatellar view B-mode 0.89 (95% confidence interval [95% CI] 0.86-0.92) and Doppler 0.55 (95% CI 0.41-0.69), medial parapatellar view B-mode 0.76 (95% CI 0.68-0.83) and Doppler 0.75 (95% CI 0.66-0.83), and lateral parapatellar view B-mode 0.82 (95% CI 0.75-0.88) and Doppler 0.76 (95% CI 0.66-0.84). CONCLUSION: A novel B-mode and Doppler image acquisition and scoring system for assessing synovitis in the pediatric knee was successfully developed through practical exercises and a consensus process. Study results demonstrate overall good-to-excellent reliability.

Protective effects of C-type natriuretic peptide on linear growth and articular cartilage integrity in a mouse model of inflammatory arthritis.

OBJECTIVE: The C-type natriuretic peptide (CNP) signaling pathway is a major contributor to postnatal skeletal growth in humans. This study was undertaken to investigate whether CNP signaling could prevent growth delay and cartilage damage in an animal model of inflammatory arthritis. METHODS: We generated transgenic mice that overexpress CNP (B6.SJL-Col2a1-NPPC) in chondrocytes. We introduced the CNP transgene into mice with experimental systemic inflammatory arthritis (K/BxN T cell receptor [TCR]) and determined the effect of CNP overexpression in chondrocytes on the severity of arthritis, cartilage damage, and linear growth. We also examined primary chondrocyte cultures for changes in gene and protein expression resulting from CNP overexpression. RESULTS: K/BxN TCR mice exhibited linear growth delay (P < 0.01) compared to controls, and this growth delay was correlated with the severity of arthritis. Diminished chondrocyte proliferation and matrix production was also seen in K/BxN TCR mice. Compared to non-CNP-transgenic mice, K/BxN TCR mice with overexpressed CNP had milder arthritis, no growth delay, and less cartilage damage. Primary chondrocytes from mice overexpressing CNP were less sensitive to inflammatory cytokines than wild-type mouse chondrocytes. CONCLUSION: CNP overexpression in chondrocytes can prevent endochondral growth delay and protect against cartilage damage in a mouse model of inflammatory arthritis. Pharmacologic or biologic modulation of the CNP signaling pathway may prevent growth retardation and protect cartilage in patients with inflammatory joint diseases, such as juvenile idiopathic arthritis.

FGFR3 promotes synchondrosis closure and fusion of ossification centers through the MAPK pathway.

Activating mutations in FGFR3 cause achondroplasia and thanatophoric dysplasia, the most common human skeletal dysplasias. In these disorders, spinal canal and foramen magnum stenosis can cause serious neurologic complications. Here, we provide evidence that FGFR3 and MAPK signaling in chondrocytes promote synchondrosis closure and fusion of ossification centers. We observed premature synchondrosis closure in the spine and cranial base in human cases of homozygous achondroplasia and thanatophoric dysplasia as well as in mouse models of achondroplasia. In both species, premature synchondrosis closure was associated with increased bone formation. Chondrocyte-specific activation of Fgfr3 in mice induced premature synchondrosis closure and enhanced osteoblast differentiation around synchondroses. FGF signaling in chondrocytes increases Bmp ligand mRNA expression and decreases Bmp antagonist mRNA expression in a MAPK-dependent manner, suggesting a role for Bmp signaling in the increased bone formation. The enhanced bone formation would accelerate the fusion of ossification centers and limit the endochondral bone growth. Spinal canal and foramen magnum stenosis in heterozygous achondroplasia patients, therefore, may occur through premature synchondrosis closure. If this is the case, then any growth-promoting treatment for these complications of achondroplasia must precede the timing of the synchondrosis closure.

Heterozygous mutations in natriuretic peptide receptor-B (NPR2) are associated with short stature.

CONTEXT: C-type natriuretic peptide (CNP) is an important regulator of skeletal growth. Loss-of-function mutations affecting the CNP receptor natriuretic peptide receptor-B (gene NPR2) cause the autosomal recessive skeletal dysplasia, acromesomelic dysplasia, Maroteaux type (AMDM). The phenotype of heterozygous carriers of NPR2 mutations is less clear. OBJECTIVE: The objective of the study was to determine the phenotypic features of heterozygous carriers of NPR2 mutations. DESIGN AND SETTING: This was a case-control study from the general community. SUBJECTS: Thirty-nine members of a family in which one member has AMDM were studied. INTERVENTION: This was an observational study. MAIN OUTCOME MEASURE: The primary measure was stature, with the hypothesis that carriers have reduced stature compared with noncarriers. RESULTS: Sixteen family members were NPR2 mutation carriers. Height z-scores of these carriers were -1.8 +/- 1.1 (mean +/- sd), which was significantly less than the 23 noncarrier family members (-0.4 +/- 0.8, P < 0.0005) and the general population (P < 0.0005). However, there was no difference in body proportion between carriers and noncarriers. The proband with AMDM had low IGF-I levels and evidence of GH resistance, as well as very high plasma levels of CNP and its amino-terminal propeptide. Levels of these peptides were normal in the heterozygous carriers. CONCLUSIONS: We have shown that heterozygous mutations in NPR2 are associated with short stature. Assuming one in 700 people unknowingly carry an NPR2 mutation, our data suggest that approximately one in 30 individuals with idiopathic short stature are carriers of NPR2 mutations.

Genetic linkage of systemic lupus erythematosus to 13q32 in African American families with affected male members.

Systemic lupus erythematosus (SLE) is a complex autoimmune disorder involving genetic and environmental factors. Previously, our group showed that SLE females with affected male relatives have higher prevalence of renal disease than SLE females with no affected male relatives in a sample of 372 individuals from 159 families. By adding 392 individuals from 181 new families, we replicated this finding in the largest collection of families with affected males, confirming our hypothesis that multiplex SLE families with at least one affected male member ("male families") comprise a distinct subpopulation of SLE multiplex families. We studied 64 male families by a genome-wide scan for SLE and found the largest signal (lod=3.08) at 13q32 in 18 African American male families using an affected-relative-pair model-free linkage method. Closer examination of IBD sharing at this region suggested a dominant mode of inheritance. Multipoint model-based linkage analysis generated a lod score of 3.13 in the same chromosomal region with a low-disease allele frequency of 0.0004 and a disease penetrance of 0.5 for the 18 African American male families. We performed fine mapping in these and three additional African American male families and the SLE predisposing locus was localized to a region tightly linked to the marker D13S892. We have therefore confirmed the linkage of SLE to 13q32, which was reported previously, and suggested that an SLE susceptibility gene in this region is specific to predisposition of African Americans to a specific form of SLE, with males at high risk.

Tapasin gene polymorphism in systemic onset juvenile rheumatoid arthritis: a family-based case-control study.

Juvenile rheumatoid arthritis (JRA) comprises a group of chronic systemic inflammatory disorders that primarily affect joints and can cause long-term disability. JRA is likely to be a complex genetic trait, or a series of such traits, with both genetic and environmental factors contributing to the risk for developing the disease and to its progression. The HLA region on the short arm of chromosome 6 has been intensively evaluated for genetic contributors to JRA, and multiple associations, and more recently linkage, has been detected. Other genes involved in innate and acquired immunity also map to near the HLA cluster on 6p, and it is possible that variation within these genes also confers risk for developing JRA. We examined the TPSN gene, which encodes tapasin, an endoplasmic reticulum chaperone that is involved in antigen processing, to elucidate its involvement, if any, in JRA. We employed both a case-control approach and the transmission disequilibrium test, and found linkage and association between the TPSN allele (Arg260) and the systemic onset subtype of JRA. Two independent JRA cohorts were used, one recruited from the Rheumatology Clinic at Cincinnati Children's Hospital Medical Center (82 simplex families) and one collected by the British Paediatric Rheumatology Group in London, England (74 simplex families). The transmission disequilibrium test for these cohorts combined was statistically significant (chi2 = 4.2, one degree of freedom; P = 0.04). Linkage disequilibrium testing between the HLA alleles that are known to be associated with systemic onset JRA did not reveal linkage disequilibrium with the Arg260 allele, either in the Cincinnati systemic onset JRA cohort or in 113 Caucasian healthy individuals. These results suggest that there is a weak association between systemic onset JRA and the TPSN polymorphism, possibly due to linkage disequilibrium with an as yet unknown susceptibility allele in the centromeric part of chromosome 6.

Dense genome-wide linkage analysis of rheumatoid arthritis, including covariates.

OBJECTIVE: Rheumatoid arthritis (RA) is a heterogeneous disease that exhibits a complex genetic component. Previous RA genome scans confirmed the involvement of the HLA region and generated data on suggestive signals at non-HLA regions, albeit with few overlaps in findings between studies. The present study was undertaken to detect potential RA gene regions and to estimate the number of true RA gene regions, taking into account the heterogeneity of RA, through performance of a dense genome scan. METHODS: In a study of 88 French Caucasian families (105 RA sibpairs), 1,088 microsatellite markers were genotyped (3.3-cM genome scan), and a multipoint model-free linkage analysis was performed. The statistical assessment of the results relied on 10,000 computer simulations. A covariate-based multipoint model-free linkage analysis was performed on the locations of regions with suggestive evidence for linkage. RESULTS: Involvement of the HLA region was strongly confirmed (P = 6 x 10(-5)), and 19 non-HLA regions showed suggestive evidence for linkage (P < 0.05); 9 of these overlapped with regions suggested in other published RA genome scans. A routine 12-cM genome scan with the same families would have detected only 7 of the 19 regions, including only 4 of the 9 overlapping regions. From the 10,000 computer simulations, we estimated that 8 +/- 4 regions (mean +/- SD) were true-positives. RA covariate-based analysis provided additional linkage evidence for 3 regions, with age at disease onset, erosions, and HLA-DRB1 shared epitope as covariates. CONCLUSION: The results of this study provide evidence of 19 non-HLA RA gene regions, with an estimate of 8 +/- 4 as true-positives, and provide additional evidence for 3 regions from covariate-based analysis.

Mutations in the transmembrane natriuretic peptide receptor NPR-B impair skeletal growth and cause acromesomelic dysplasia, type Maroteaux.

The homodimeric transmembrane receptor natriuretic peptide receptor B (NPR-B [also known as guanylate cyclase B, GC-B, and GUC2B]; gene name NPR2) produces cytoplasmic cyclic GMP from GTP on binding its extracellular ligand, C-type natriuretic peptide (CNP). CNP has previously been implicated in the regulation of skeletal growth in transgenic and knockout mice. The autosomal recessive skeletal dysplasia known as "acromesomelic dysplasia, type Maroteaux" (AMDM) maps to an interval that contains NPR2. We sequenced DNA from 21 families affected by AMDM and found 4 nonsense mutations, 4 frameshift mutations, 2 splice-site mutations, and 11 missense mutations. Molecular modeling was used to examine the putative protein change brought about by each missense mutation. Three missense mutations were tested in a functional assay and were found to have markedly deficient guanylyl cyclase activity. We also found that obligate carriers of NPR2 mutations have heights that are below the mean for matched controls. We conclude that, although NPR-B is expressed in a number of tissues, its major role is in the regulation of skeletal growth.