CNOT1 p.Arg535Cys variant in holoprosencephaly with late onset diabetes mellitus.

Holoprosencephaly (HPE) results from a lack of cleavage of the prosencephalon. It has a complex etiology, resulting from chromosome abnormalities or single gene variants in the Sonic hedgehog signaling pathway. A single variant, p.Arg535Cys in CNOT1, has been described in HPE in association with pancreatic agenesis and neonatal diabetes. Here, we report on a case of HPE and p.Arg535Cys in CNOT1 without pancreatic agenesis where the patient presented with diabetes mellitus in adolescence. This case reinforces the role of CNOT1 in pancreatic development. We suggest that individuals with p.Arg535Cys in CNOT1 with no pancreas abnormalities observed at birth should be screened for diabetes during follow-up.

Challenges and recommendations to increasing the use of exome sequencing and whole genome sequencing for diagnosing rare diseases in Brazil: an expert perspective.

Early diagnosis of genetic rare diseases is an unmet need in Brazil, where an estimated 10-13 million people live with these conditions. Increased use of chromosome microarray assays, exome sequencing, and whole genome sequencing as first-tier testing techniques in suitable indications can shorten the diagnostic odyssey, eliminate unnecessary tests, procedures, and treatments, and lower healthcare expenditures. A selected panel of Brazilian experts in fields related to rare diseases was provided with a series of relevant questions to address before a multi-day conference. Within this conference, each narrative was discussed and edited through numerous rounds of discussion until agreement was achieved. The widespread adoption of exome sequencing and whole genome sequencing in Brazil is limited by various factors: cost and lack of funding, reimbursement, awareness and education, specialist shortages, and policy issues. To reduce the burden of rare diseases and increase early diagnosis, the Brazilian healthcare authorities/government must address the barriers to equitable access to early diagnostic methods for these conditions. Recommendations are provided, including broadening approved testing indications, increasing awareness and education efforts, increasing specialist training opportunities, and ensuring sufficient funding for genetic testing.

The Minimum Data Set for Rare Diseases: Systematic Review.

BACKGROUND: The minimum data set (MDS) is a collection of data elements to be grouped using a standard approach to allow the use of data for clinical and research purposes. Health data are typically voluminous, complex, and sometimes too ambiguous to generate indicators that can provide knowledge and information on health. This complexity extends further to the rare disease (RD) domain. MDSs are essential for health surveillance as they help provide services and generate recommended population indicators. There is a bottleneck in international literature that reveals a global problem with data collection, recording, and structuring in RD. OBJECTIVE: This study aimed to identify and analyze the MDSs used for RD in health care networks worldwide and compare them with World Health Organization (WHO) guidelines. METHODS: The population, concept, and context methodology proposed by the Joanna Briggs Institute was used to define the research question of this systematic review. A total of 4 databases were reviewed, and all the processes were reported using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology. The data elements were analyzed, extracted, and organized into 10 categories according to WHO digital health guidelines. The quality assessment used the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) checklist. RESULTS: We included 20 studies in our review, 70% (n=14) of which focused on a specific health domain and 30% (n=6) of which referred to RD in general. WHO recommends that health systems and networks use standard terminology to exchange data, information, knowledge, and intelligence in health. However, there was a lack of terminological standardization of the concepts in MDSs. Moreover, the selected studies did not follow the same standard structure for classifying the data from their MDSs. All studies presented MDSs with limitations or restrictions because they covered only a specific RD, or their scope of application was restricted to a specific context or geographic region. Data science methods and clinical experience were used to design, structure, and recommend a fundamental global MDS for RD patient records in health care networks. CONCLUSIONS: Our study highlights the difficulties in standardizing and categorizing findings from MDSs for RD because of the varying structures used in different studies. The fundamental RD MDS designed in this study comprehensively covers the data needs in the clinical and management sectors. These results can help public policy makers support other aspects of their policies. We highlight the potential of our results to help strategic decisions related to RD. TRIAL REGISTRATION: PROSPERO CRD42021221593; https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=221593. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): RR2-10.1016/j.procs.2021.12.034.

Achondroplasia in Latin America: practical recommendations for the multidisciplinary care of pediatric patients.

BACKGROUND: Achondroplasia is the most common bone dysplasia associated with disproportionate short stature, and other comorbidities, such as foramen magnum stenosis, thoracolumbar kyphosis, lumbar hyperlordosis, genu varum and spinal compression. Additionally, patients affected with this condition have higher frequency of sleep disorders, ear infections, hearing loss and slowed development milestones. Considering these clinical features, we aimed to summarize the regional experts' recommendations for the multidisciplinary management of patients with achondroplasia in Latin America, a vast geographic territory with multicultural characteristics and with socio-economical differences of developing countries. METHODS: Latin American experts (from Argentina, Brazil, Chile and Colombia) particiáted of an Advisory Board meeting (October 2019), and had a structured discussion how patients with achondroplasia are followed in their healthcare centers and punctuated gaps and opportunities for regional improvement in the management of achondroplasia. RESULTS: Practical recommendations have been established for genetic counselling, prenatal diagnosis and planning of delivery in patients with achondroplasia. An outline of strategies was added as follow-up guidelines to specialists according to patient developmental phases, amongst them neurologic, orthopedic, otorhinolaryngologic, nutritional and anthropometric aspects, and related to development milestones. Additionally, the role of physical therapy, physical activity, phonoaudiology and other care related to the quality of life of patients and their families were discussed. Preoperative recommendations to patients with achondroplasia were also included. CONCLUSIONS: This study summarized the main expert recommendations for the health care professionals management of achondroplasia in Latin America, reinforcing that achondroplasia-associated comorbidities are not limited to orthopedic concerns.

PIGF deficiency causes a phenotype overlapping with DOORS syndrome.

DOORS syndrome is characterized by deafness, onychodystrophy, osteodystrophy, intellectual disability, and seizures. In this study, we report two unrelated individuals with DOORS syndrome without deafness. Exome sequencing revealed a homozygous missense variant in PIGF (NM_173074.3:c.515C>G, p.Pro172Arg) in both. We demonstrate impaired glycosylphosphatidylinositol (GPI) biosynthesis through flow cytometry analysis. We thus describe the causal role of a novel disease gene, PIGF, in DOORS syndrome and highlight the overlap between this condition and GPI deficiency disorders. For each gene implicated in DOORS syndrome and/or inherited GPI deficiencies, there is considerable clinical variability so a high index of suspicion is warranted even though not all features are noted.

Early-onset nucleotide excision repair disorders with neurological impairment: Clues for early diagnosis and prognostic counseling.

Nucleotide excision repair associated diseases comprise overlapping phenotypes and a wide range of outcomes. The early stages still remain under-investigated and underdiagnosed, even although an early recognition of the first symptoms is of utmost importance for appropriate care and genetic counseling. We systematically collected clinical and molecular data from the literature and from newly diagnosed NER patients with neurological impairment, presenting clinical symptoms before the age of 12 months, including foetal cases. One hundred and eighty-five patients were included, 13 with specific symptoms during foetal life. Arthrogryposis, microcephaly, cataracts, and skin anomalies are the most frequently reported signs in early subtypes. Non ERCC6/CSB or ERCC8/CSA genes are overrepresented compared to later onset cohorts: 19% patients of this cohort presented variants in ERCC1, ERCC2/XPD, ERCC3/XPB or ERCC5/XPG. ERCC5/XPG is even the most frequently involved gene in foetal cases (10/13 cases, [4/7 families]). In this cohort, the mutated gene, the age of onset, the type of disease, severe global developmental delay, IUGR and skin anomalies were associated with earlier death. This large survey focuses on specific symptoms that should attract the attention of clinicians towards early-onset NER diagnosis in foetal and neonatal period, without waiting for the completeness of classical criteria.

Osteogenesis imperfecta and hearing loss: an analysis of patients attended at a benchmark treatment center in southern Brazil.

OBJECTIVE: To characterize the audiological findings of a sample of patients with osteogenesis imperfecta (OI) in southern Brazil. METHODS: This was a cross-sectional, observational, quantitative study. Research was carried out at a hospital which is considered to offer benchmark treatment for patients with OI in southern Brazil. Seventy-seven patients were recruited, at ages between 5 and 55 years; the mean age was 21.9 ± 14.3 years. Patients were divided into three age groups: 10 and under, 10-19 and over 19. During our study, peripheral audiological assessments were performed (pure tone testing and acoustic immittance measurements). The main outcome measures taken into account were airway thresholds, bone conduction, air-bone gap and compliance values between compared frequencies. Data were analyzed per ear. RESULTS: Normal hearing thresholds were found in 96 (64.4%) ears of the total sample. When analysis was stratified into age groups, normal hearing thresholds were found in 81.3%, 65%, and 54.4%, of the children, adolescent and adult groups, respectively. Concerning hearing impairments, there was a predominance of mixed type hearing loss in adults (21.1%) whereas adolescents presented conductive hearing loss or a conductive loss factor, while maintaining airway thresholds within the bounds of normality (30%). Ears with hearing loss showed superior compliance means than ears without hearing loss (p = 0.002). CONCLUSIONS: Overall, the majority of the subjects in this patient sample presented normal hearing thresholds. When present, hearing impairments were more prevalent in the adult group than in the adolescent or children's groups.

Cyclic pamidronate treatment for osteogenesis imperfecta: Report from a Brazilian reference center.

Treatment of moderate and severe forms of osteogenesis imperfecta (OI) with cyclic pamidronate at the Reference Center for OI Treatment in Southern Brazil was studied. A retrospective cohort study was conducted from 2002 to 2012. Data were obtained during inpatient (drug infusion) and outpatient care. Clinical data, including the presence of blue sclerae, dentinogenesis imperfecta, history and site of the fractures, biochemical data, including calcium, phosphorus, and alkaline phosphatase levels, were systematically collected. Bone mineral density (BMD) was measured using dual energy X-ray absorptiometry (DXA). Forty-five patients (26 females) were included in the study, and the age of the patients at the time of diagnosis ranged from 1 to 144 months, with a median age (p25-p75) of 38 (5-96) months. Most cases presented OI-4 (51.1%), and the median age of the patients at the start of treatment was 3.3 years (25-75 percentiles: 0.5 - 8.7 years). Twenty-four patients (54.5%) had some adverse events or intercurrences during treatment, and the treatment compliance mean was 92.3% (± 10.7). The treatment with intravenous pamidronate has shown to be safe, well-tolerated, and effective in regard to the improvement of BMD and the reduction of the number of fractures in children and adolescents with OI.

Health-related quality of life of children and adolescents with osteogenesis imperfecta: a cross-sectional study using PedsQL™.

BACKGROUND: Osteogenesis imperfecta (OI) is a disorder of bone formation leading to low mineral density and fractures. Children and adolescents with OI require periodic medical follow up, corrective surgery, drug therapy and physical therapy, as well as specific daily care practices. In addition, they have an increased incidence of fractures, which require immobilization and cause severe discomfort and short-term disability. This study evaluated the health-related quality of life of children and adolescents with OI in two reference centers for OI treatment in southern Brazil. METHODS: In this prospective cross-sectional study, the Pediatric Quality of Life Inventory (PedsQLTM) was applied in two university-affiliated reference centers for OI treatment in southern Brazil. Children and adolescents aged ≥ 5 years with clinical diagnoses of OI were included. Clinical data and socioeconomic status was evaluated. RESULTS: The sample consisted of 52 children and adolescents with OI (aged 5-17 years); 26 (50%) participants with type I OI, 13 (25%) type IV, 12 (23.1 %) type III, and 1 (1.9%) type V OI. Physical and social functioning domains differed significantly according to clinical presentation of OI with lowest scores in the severe type (OI type III). Pain seems to be the variable that is most associated with impact on the PedsQL domains. CONCLUSIONS: Overall, this study revealed differences in physical functioning and social functioning in relation to OI clinical presentation. These results reinforcing the importance of the clinical management of these patients with the aim of functional improvement and importance of pain control.

An etiologic regulatory mutation in IRF6 with loss- and gain-of-function effects.

DNA variation in Interferon Regulatory Factor 6 (IRF6) causes Van der Woude syndrome (VWS), the most common syndromic form of cleft lip and palate (CLP). However, an etiologic variant in IRF6 has been found in only 70% of VWS families. To test whether DNA variants in regulatory elements cause VWS, we sequenced three conserved elements near IRF6 in 70 VWS families that lack an etiologic mutation within IRF6 exons. A rare mutation (350dupA) was found in a conserved IRF6 enhancer element (MCS9.7) in a Brazilian family. The 350dupA mutation abrogated the binding of p63 and E47 transcription factors to cis-overlapping motifs, and significantly disrupted enhancer activity in human cell cultures. Moreover, using a transgenic assay in mice, the 350dupA mutation disrupted the activation of MCS9.7 enhancer element and led to failure of lacZ expression in all head and neck pharyngeal arches. Interestingly, disruption of the p63 Motif1 and/or E47 binding sites by nucleotide substitution did not fully recapitulate the effect of the 350dupA mutation. Rather, we recognized that the 350dupA created a CAAAGT motif, a binding site for Lef1 protein. We showed that Lef1 binds to the mutated site and that overexpression of Lef1/ß-Catenin chimeric protein repressed MCS9.7-350dupA enhancer activity. In conclusion, our data strongly suggest that 350dupA variant is an etiologic mutation in VWS patients and disrupts enhancer activity by a loss- and gain-of-function mechanism, and thus support the rationale for additional screening for regulatory mutations in patients with CLP.

Study of the Determinants of Vitamin D Status in Pediatric Patients With Osteogenesis Imperfecta.

OBJECTIVE: Vitamin D is essential to the development and maintenance of the skeleton, especially for children with bone disorders such as osteogenesis imperfecta (OI). We evaluated serum 25-hydroxyvitamin D (25-OHD) levels to assess the relationship between determinants of vitamin D status in pediatric patients with OI. METHODS: This cross-sectional study evaluated sex, age, weight, height, body mass index, OI type, sunscreen use, season of assessment, sun exposure, vitamin D and calcium supplementation, bisphosphonate treatment, bone mineral density (BMD), milk and soda consumption, mobility, and time of sedentary activity. Levels of serum 25-OHD, calcium, parathyroid hormone (PTH), phosphorus, and alkaline phosphatase (ALP) were analyzed. Serum levels of 25-OHD were classified according to sufficient (>30 ng/ml or 75 nmol/L), insufficient (20-30 ng/ml or 50-75 nmol/L), moderately deficient (20-10 ng/ml or 50-25 nmol/L), and severely deficient (<10 ng/ml or 25 nmol/L). RESULTS: Fifty-two patients were included and 46 (88.4%) were classified as having insufficient or deficient 25-OHD. An inverse correlation between serum 25-OHD and time of sedentary activity (r = -0.597, p < 0.001) and a positive correlation with height (r = 0.521, p = 0.046) and whole body BMD (r = 0.586, p = 0.022) were observed. A significant difference between the number of glasses of milk consumed (p = 0.010) was observed. CONCLUSION: To optimize bone health, patients with OI need to be educated regarding habits that can improve serum 25-OHD levels, such as a reduction in periods of inactivity, the importance of sun exposure, and increasing consumption of milk and fortified dairy products.

Rare Variants in the Epithelial Cadherin Gene Underlying the Genetic Etiology of Nonsyndromic Cleft Lip with or without Cleft Palate.

Nonsyndromic orofacial cleft (NSOFC) is a complex disease of still unclear genetic etiology. To investigate the contribution of rare epithelial cadherin (CDH1) gene variants to NSOFC, we target sequenced 221 probands. Candidate variants were evaluated via in vitro, in silico, or segregation analyses. Three probably pathogenic variants (c.760G>A [p.Asp254Asn], c.1023T>G [p.Tyr341*], and c.2351G>A [p.Arg784His]) segregated according to autosomal dominant inheritance in four nonsyndromic cleft lip with or without cleft palate (NSCL/P) families (Lod score: 5.8 at θ = 0; 47% penetrance). A fourth possibly pathogenic variant (c.387+5G>A) was also found, but further functional analyses are needed (overall prevalence of CDH1 candidate variants: 2%; 15.4% among familial cases). CDH1 mutational burden was higher among probands from familial cases when compared to that of controls (P = 0.002). We concluded that CDH1 contributes to NSCL/P with mainly rare, moderately penetrant variants, and CDH1 haploinsufficiency is the likely etiological mechanism.

Clinical and molecular characterization of a Brazilian cohort of campomelic dysplasia patients, and identification of seven new SOX9 mutations.

Campomelic dysplasia (CD) is an autosomal, dominantly inherited, skeletal abnormality belonging to the subgroup of bent bone dysplasias. In addition to bowed lower limbs, CD typically includes the following: disproportionate short stature, flat face, micrognathia, cleft palate, bell-shaped thorax, and club feet. Up to three quarters of 46, XY individuals may be sex-reversed. Radiological signs include scapular and pubic hypoplasia, narrow iliac wings, spaced ischia, and bowed femora and tibiae. Lethal CD is usually due to heterozygous mutations in SOX9, a major regulator of chondrocytic development. We present a detailed clinical and molecular characterization of nine Brazilian CD patients. Infants were either stillborn (n = 2) or died shortly after birth and presented similar phenotypes. Sex-reversal was observed in one of three chromosomally male patients. Sequencing of SOX9 revealed new heterozygous mutations in seven individuals. Six patients had mutations that resulted in premature transcriptional termination, while one infant had a single-nucleotide substitution at the conserved splice-site acceptor of intron 1. No clear genotype-phenotype correlations were observed. This study highlights the diversity of SOX9 mutations leading to lethal CD, and expands the group of known genetic alterations associated with this skeletal dysplasia.

Molecular analysis of holoprosencephaly in South America.

Holoprosencephaly (HPE) is a spectrum of brain and facial malformations primarily reflecting genetic factors, such as chromosomal abnormalities and gene mutations. Here, we present a clinical and molecular analysis of 195 probands with HPE or microforms; approximately 72% of the patients were derived from the Latin American Collaborative Study of Congenital Malformations (ECLAMC), and 82% of the patients were newborns. Alobar HPE was the predominant brain defect in almost all facial defect categories, except for patients without oral cleft and median or lateral oral clefts. Ethmocephaly, cebocephaly, and premaxillary agenesis were primarily observed among female patients. Premaxillary agenesis occurred in six of the nine diabetic mothers. Recurrence of HPE or microform was approximately 19%. The frequency of microdeletions, detected using Multiplex Ligation-dependant Probe Amplification (MLPA) was 17% in patients with a normal karyotype. Cytogenetics or QF-PCR analyses revealed chromosomal anomalies in 27% of the probands. Mutational analyses in genes SHH, ZIC2, SIX3 and TGIF were performed in 119 patients, revealing eight mutations in SHH, two mutations in SIX3 and two mutations in ZIC2. Thus, a detailed clinical description of new HPE cases with identified genetic anomalies might establish genotypic and phenotypic correlations and contribute to the development of additional strategies for the analysis of new cases.

Muscle strength, joint range of motion, and gait in children and adolescents with osteogenesis imperfecta.

PURPOSE: To analyze clinical and functional features of children and adolescents with osteogenesis imperfecta (OI). METHODS: A cross-sectional study of 62 participants examined clinical, body structure and function and activity features. RESULTS: A total of 31 participants had OI type I, 9 had type III, and 22 had type IV. Mild (type I) and moderate/severe (types III and IV) OI differed significantly in occurrence of fractures, presence of bone deformities, the use of intramedullary rods, bone mineral density, and bisphosphonate therapy. Age of gait acquisition showed an association with overall joint range of motion and an inverse relationship with overall muscle strength. Level of ambulation was associated with overall muscle strength and inversely associated with overall joint range of motion. CONCLUSIONS: Features vary according to OI type. Moderate and severe forms of OI are associated with greater functional limitation, influenced by fracture history, which negatively affects the acquisition and level of ambulation.

Evaluation of functioning and associated factors in children and adolescents with osteogenesis imperfecta.

OBJECTIVE: The aim of this study was to evaluate the functioning and associated factors in children and adolescents with osteogenesis imperfecta (OI). METHODS: This is a cross-sectional study conducted on 30 children and adolescents with OI. Medical records, use of bisphosphonates, socioeconomic status, handgrip strength, balance, joint hypermobility, ambulatory level, and the Pediatric Evaluation of Disability Inventory-Computer Adaptative Test (PEDI-CAT) scores were assessed. Data is presented as mean and standard deviation and Student's t-test or Mann-Whitney U test. Categorical data is presented as frequency and analyzed using Fisher's exact test. Within-group analyses were conducted using ANCOVA or Wilcoxon signed-rank test. Correlations used Kendall's Tau-b test. RESULTS: The participants involved in this study were 6-18 years old. The sample was separated into two groups according to disease severity. The moderate/severe OI group (n=10) presented a lower height and muscular strength than the mild group (n=20). Muscle weakness was observed in all participants with OI when compared with the normal population. No differences were observed between the groups in the PEDI-CAT scores except for the mobility domain. There were correlations between the PEDI-CAT mobility domain and the number of fractures, OI type, weight, and balance; there was also a correlation between the PEDI-CAT daily activities, mobility, responsibility, and social/cognitive domains. CONCLUSIONS: The findings suggest that children with moderate/severe forms of OI can achieve the same function levels as children with mild OI. Fractures can have a major influence on the functional level, and treatment should focus on the prevention and rehabilitation of these events when they occur.

Building a National Policy for Rare Disease in Brazil.

Rare diseases (RD) are individually rare, although encompass a significant proportion of the population, affecting not only the individuals but also their families. In Brazil RD is defined by the Ministry of Health as a disorder that affects up to 65 individuals in 100,000, or 1.3 individuals in every 2,000. In this review the environment that led to the publication of a National Policy for Comprehensive Care for People of Rare Disease in 2014, a national plan with the aim to decrease morbidity and mortality of RD, improving the care of people with RD in the public health system are described. The process that finally led to such policy took over a decade, moving forward not only due to technical needs, but having patient organizations as essential actors and advocates. Specialized centers in RD were licensed and, since its publication, 33 centers have been accredited; such process, however, has been slow and concentrated in specific regions and larger cities of the country. Despite the incorporation of genetic tests in 2014 and exome sequencing later in 2020, many genetic tests are not offered by specialized centers, with unequal availability across the country. Public health system in Brazil uses ICD-10 for disease coding, preventing appropriate epidemiologic knowledge of RD in Brazil. Incorporation of new technologies as orphan drugs has been in place and regulation for expedite licensing for new RD drugs were issued, although high cost and availability to RD population has been a challenge.

Medical Genetics in Brazil in the 21st Century: A Thriving Specialty and Its Incorporation in Public Health Policies.

Brazil is a continent-size country with 203 million inhabitants, classified as a developing upper-middle-income country, although inequities remain significant. Most of the population is assisted by the public Unified Health System (SUS), along with a thriving private health sector. Congenital malformations are the second leading cause of infant mortality and chronic/genetic disorders and a significant burden in hospital admissions. The past two decades have been crucial for formalizing medical genetics as a recognized medical specialty in the SUS, as well as for implementing a new health policy by the Ministry of Health for comprehensive care for rare diseases. These public health policies had the broad support of the Brazilian Society of Medical Genetics and Genomics and patient organizations. Most comprehensive genetic services are concentrated in large urban centers in the South and Southeast regions of Brazil; with this new policy, new services throughout the country are progressively being integrated. The number of medical geneticists increased by 103% in a decade. Details on the policy and an overview of the availability of services, testing, human resources, newborn screening, research projects, patient organizations, and relevant issues regarding medical genetics in this vast and diverse country are presented.

Access to genetic evaluation of 1463 individuals with orofacial cleft in Brazil.

OBJECTIVE: The current study delves into the accessibility of genetic evaluations for individuals with orofacial clefts (OC), comparing data between genetics and treatment centers across Brazil. METHODS: This cross-sectional retrospective study analyzed primary data from 1463 OC individuals registered in the Brazilian Database of Craniofacial Anomalies (BDCA) between 2008 and 2018 without age or sex selection. Diagnostic exam results stemming from research projects until 2023 were considered. RESULTS: Of the 1463 individuals with typical OC, 987 were non-syndromic, 462 were syndromic (SOC), 10 presented atypical forms, and three were not specified OC cases. The average age for accessing laboratory diagnosis was 8.5 years among SOC individuals. Notably, more SOC cases were registered in genetics centers than treatment and rehabilitation centers (37.1 % vs. 29 %, p = 0.0015). Those originating from genetics centers accessed diagnosis at an average age of 7.3 years, while those from treatment and rehabilitation centers experienced delays with an average age of 10.7 years (p = 0.0581). CONCLUSIONS: Irrespective of the center of origin, the data highlight delayed diagnosis and challenges in accessing genetic tests for the syndromic group. Given the widespread reliance on the public health system by most of the Brazilian population, disseminating this data can significantly contribute to shaping an informed perspective on healthcare access. These insights can improve public policies tailored to the unique needs of individuals with OC.

Identification of a founder effect involving n.197C>T variant in RMRP gene associated to cartilage-hair hypoplasia syndrome in Brazilian patients.

Cartilage-hair hypoplasia syndrome (CHH) is an autosomal recessive disorder frequently linked to n.72A>G (previously known as n.70A>G and n.71A>G), the most common RMRP variant worldwide. More than 130 pathogenic variants in this gene have already been described associated with CHH, and founder alterations were reported in the Finnish and Japanese populations. Our previous study in Brazilian CHH patients showed a high prevalence of n.197C>T variant (former n.195C>T and n.196C>T) when compared to other populations. The aim of this study was to investigate a possible founder effect of the n.197C>T variant in the RMRP gene in a series of CHH Brazilian patients. We have selected four TAG SNPs within chromosome 9 and genotyped the probands and their parents (23 patients previously described and nine novel). A common haplotype to the n.197C>T variant carriers was identified. Patients were also characterized for 46 autosomal Ancestry Informative Markers (AIMs). European ancestry was the most prevalent (58%), followed by African (24%) and Native American (18%). Our results strengthen the hypothesis of a founder effect for the n.197C>T variant in Brazil and indicate that this variant in the RMRP gene originated from a single event on chromosome 9 with a possible European origin.