Molecular and phenotypic characteristics of Bardet-Biedl syndrome in Chinese patients.

BACKGROUND: Bardet-Biedl syndrome (BBS) is a type of non-motile ciliopathy. To date, 26 genes have been reported to be associated with BBS. However, BBS is genetically heterogeneous, with significant clinical overlap with other ciliopathies, which complicates diagnosis. Disability and mortality rates are high in BBS patients; therefore, it is urgent to improve our understanding of BBS. Thus, our study aimed to describe the genotypic and phenotypic spectra of BBS in China and to elucidate genotype-phenotype correlations. METHODS: Twenty Chinese patients diagnosed with BBS were enrolled in this study. We compared the phenotypes of Chinese BBS patients in this study with those from other countries to analyze the phenotypic differences across patients worldwide. In addition, genotype-phenotype correlations were described for our cohort. We also summarized all previously reported cases of BBS in Chinese patients (71 patients) and identified common and specific genetic variants in the Chinese population. RESULTS: Twenty-eight variants, of which 10 are novel, in 5 different BBS-associated genes were identified in 20 Chinese BBS patients. By comparing the phenotypes of BBSome-coding genes (BBS2,7,9) with those of chaperonin-coding genes (BBS10,12), we found that patients with mutations in BBS10 and 12 had an earlier age of onset (1.10 Vs. 2.20, p < 0.01) and diagnosis (4.64 Vs. 13.17, p < 0.01), whereas patients with mutations in BBS2, 7, and 9 had a higher body mass index (28.35 Vs. 24.21, p < 0.05) and more vision problems (p < 0.05). Furthermore, in 91 Chinese BBS patients, mutations were predominant in BBS2 (28.89%) and BBS7 (15.56%), and the most frequent variants were in BBS2: c.534 + 1G > T (10/182 alleles) and BBS7: c.1002delT (7/182 alleles), marking a difference from the genotypic spectra of BBS reported abroad. CONCLUSIONS: We recruited 20 Chinese patients with BBS for genetic and phenotypic analyses, and identified common clinical manifestations, pathogenic genes, and variants. We also described the phenotypic differences across patients worldwide and among different BBS-associated genes. This study involved the largest cohort of Chinese patients with BBS, and provides new insights into the distinctive clinical features of specific pathogenic variants.

Ocular impairment as the first and only manifestation of Bardet-Biedl syndrome: A case report.

Bardet-Biedl syndrome is a ciliopathy mainly associated with retinal dystrophy, renal dysfunction, post-axial polydactyly, obesity, cognitive deficit and hypogonadism. The symptoms associated with retinal dystrophy do not usually appear until the first decade of life, so the diagnosis is usually delayed. Ocular involvement may be the initial form of manifestation of this syndrome, it may even be the only one, so it should be taken into account in the differential diagnosis of amblyopia in a child who does not improve despite correct compliance with treatment. A case of low visual acuity in a pediatric patient is presented as an initial manifestation that leads to the diagnosis of Bardet-Biedl Syndrome, and which is also the only symptom that the patient presents to date, despite being a multisystem disease.

Bardet-Biedl syndrome: A clinical overview focusing on diagnosis, outcomes and best-practice management.

Bardet-Biedl syndrome (BBS) is a genetic disorder characterized by early-onset obesity, polydactyly, genital and kidney anomalies, developmental delay and vision loss due to rod-cone dystrophy. BBS is an autosomal recessive disorder with >20 implicated genes. The genotype-phenotype relationship in BBS is not clear, and there may be additional modifying factors. The underlying mechanism is dysfunction of primary cilia. In BBS, receptor trafficking in and out of the cilia is compromised, affecting multiple organ systems. Along with early-onset obesity, hyperphagia is a prominent symptom and contributes significantly to clinical morbidity and caregiver burden. While there is no cure for BBS, setmelanotide is a new pharmacotherapy approved for treatment of obesity in BBS. The differential diagnosis for BBS includes other ciliopathies, such as Alstrom syndrome, and other genetic obesity syndromes, such as Prader-Willi syndrome. Careful clinical history and genetic testing can help determine the diagnosis and a multidisciplinary team is necessary to guide clinical management.

Serum Ghrelin and Glucagon-like Peptide 1 Levels in Children with Prader-Willi and Bardet-Biedl Syndromes

Objective: Prader-Willi syndrome (PWS) and Bardet-Biedl syndrome (BBS) are causes of pediatric syndromic obesity. We aimed to investigate a possible role for ghrelin and glucagon-like peptide-1 (GLP-1) in the pathophysiology of PWS and BBS. Methods: The study included 12 children with PWS, 12 children with BBS, 13 pediatric obese controls (OC) and 12 pediatric lean controls (LC). Fasting serum ghrelin and GLP-1 levels were measured by ELISA. Results: In the PWS group, no significant difference was detected for median ghrelin levels when compared with OC and LC, which were 0.96 (0.69-1.15), 0.92 (0.72-1.20) and 1.13 (0.84-1.29) ng/mL, respectively. Similarly, there was no difference in PWS median GLP-1 levels when compared with OC and LC; 1.86 (1.5-2.94), 2.24 (1.62-2.78) and 2.06 (1.8-3.41) ng/mL, respectively. In the BBS group, there was no difference in median ghrelin levels when compared with OC and LC; 1.05 (0.87-1.51), 0.92 (0.72-1.20) and 1.13 (0.84-1.29) ng/mL, respectively. Neither was there a significant difference in median GLP-1 levels; 2.46 (1.91-4.17), 2.24 (1.62-2.78) and 2.06 (1.8-3.41) ng/mL for BBS, OC and LC, respectively. Conclusion: There were no differences in median fasting ghrelin or GLP-1 levels when comparing patients with PWS and BBS with obese or lean peers. However, similar studies with larger series are needed.

Retinal nerve fibre layer thinning and corneal nerve loss in patients with Bardet-Biedl syndrome.

BACKGROUND: Bardet-Biedl syndrome (BBS) is an autosomal recessive, genetically heterogeneous, pleiotropic disorder caused by variants in genes involved in the function of the primary cilium. We have harnessed genomics to identify BBS and ophthalmic technologies to describe novel features of BBS. CASE PRESENTATION: A patient with an unclear diagnosis of syndromic type 2 diabetes mellitus, another affected sibling and unaffected siblings and parents were sequenced using DNA extracted from saliva samples. Corneal confocal microscopy (CCM) and retinal spectral domain optical coherence tomography (SD-OCT) were used to identify novel ophthalmic features in these patients. The two affected individuals had a homozygous variant in C8orf37 (p.Trp185*). SD-OCT and CCM demonstrated a marked and patchy reduction in the retinal nerve fiber layer thickness and loss of corneal nerve fibers, respectively. CONCLUSION: This report highlights the use of ophthalmic imaging to identify novel retinal and corneal abnormalities that extend the phenotype of BBS in a patient with syndromic type 2 diabetes.

Sequence variants in different genes underlying Bardet-Biedl syndrome in four consanguineous families.

BACKGROUND: Bardet-Biedl Syndrome (BBS) is a rare (1:13,500-1-160,000) heterogeneous congenital disorder, characterized by postaxial polydactyly, obesity, hypogonadism, rod-cone dystrophy, cognitive impairment, and renal abnormalities (renal cystic dysplasia, anatomical malformation). To date about twenty-five genes have been identified to cause BBS, which accounts for about 80% of BBS diagnosis. METHODS: In the current study, we have performed mutational screening of four Pakistani consanguineous families (A-D) with clinical manifestation of BBS by microsatellite-based genotyping and whole exome sequencing. RESULTS: Analysis of the data revealed four variants, including a novel/unique inheritance pattern of compound heterozygous variants, p.(Ser40*) and p.(Thr259Leufs*21), in MKKS gene, novel homozygous variant, p.(Gly251Val)] in BBS7 gene and two previously reported p.(Thr259Leufs*21) in MKKS and p.(Met1Lys) in BBS5 gene. The variants were found segregated with the disorder within the families. CONCLUSION: The study not only expanded mutations spectrum in the BBS genes, but this will facilitate diagnosis and genetic counselling of families carrying BBS related phenotypes in Pakistani population.

Searching for Effective Methods of Diagnosing Nervous System Lesions in Patients with Alström and Bardet-Biedl Syndromes.

Bardet-Biedl syndrome (BBS) and Alström syndrome (ALMS) are rare multisystem diseases with an autosomal recessive mode of inheritance and genetic heterogeneity, characterized by visual impairment, hearing impairment, cardiomyopathy, childhood obesity, and insulin resistance. The purpose of our study was to evaluate the indicators of nervous system changes occurring in patients with ALMS and BBS using optical coherence tomography (OCT) and magnetic resonance spectroscopy (MRS) methods compared to a group of healthy subjects. The OCT results showed significantly lower macular thickness in the patient group compared to the control group (p = 0.002). The MRS study observed differences in metabolite levels between the study and control groups in brain areas such as the cerebellum, thalamus, and white matter. After summing the concentrations from all areas, statistically significant results were obtained for N-acetylaspartate, total N-acetylaspartate, and total creatine. Concentrations of these metabolites were reduced in ALMS/BBS patients by 38% (p = 0.0004), 35% (p = 0.0008), and 28% (p = 0.0005), respectively. Our results may help to understand the pathophysiology of these rare diseases and identify strategies for new therapies.

Caregiver burden in Bardet-Biedl syndrome: findings from the CARE-BBS study.

BACKGROUND: Bardet-Biedl syndrome (BBS) is a rare, genetically heterogeneous obesity syndrome associated with hyperphagia. Given the early onset of BBS symptoms in childhood and multifaceted complications, this study aimed to quantify the caregiver burden associated with BBS. METHODS: A cross-sectional, multi-country survey of caregivers from the United States (US), United Kingdom (UK), Canada, and Germany was designed to quantify the extent of caregiver burden associated with obesity and hyperphagia symptoms (i.e., uncontrollable hunger) among patients with BBS. RESULTS: A total of 242 caregivers across the four countries met the inclusion criteria and completed the survey. The mean (standard deviation [SD]) age of the caregivers was 41.9 (6.7) years, and the mean (SD) age of individuals with BBS in their care was 12.0 (3.7) years. Hyperphagia contributed to a BBS diagnosis in 230 of 242 individuals (95.0%). On average, caregivers used eight different weight management approaches for those in their care and expressed a strong desire for more effective weight management methods. Based on the Impacts of Hyperphagia: Caregiver version, patients' hyperphagia had a moderate-to-severe impact on caregiver mood (56.6%), sleep (46.6%), and relationships (48.0%). Caregivers reported experiencing a high level of personal strain (mean [SD], 17.1 [2.9]) and family impact (mean [SD] score, 26.0 [3.8]) due to BBS, as measured by the Revised Impact on Family Scale. Among caregivers in the workforce, there also was high impairment in total work productivity (mean [SD], 60.9% [21.4%]) due to caring for patients with BBS according to the Work Productivity and Activity Impairment. More than half (53%) of the caregivers reported spending over 5,000 out-of-pocket in local currency for medical expenses for the patient with BBS in their care. CONCLUSIONS: Obesity and hyperphagia have negative impacts on the lives of caregivers of patients with BBS. The burden is demonstrated to be multifaceted, with various components that may interact with and confound each other, including intensive weight management efforts, productivity loses, impaired family dynamics and out-of-pocket medical expenses.

Exome sequencing in a Romanian Bardet-Biedl syndrome cohort revealed an overabundance of causal BBS12 variants.

Bardet-Biedl syndrome (BBS), is an emblematic ciliopathy hallmarked by pleiotropy, phenotype variability, and extensive genetic heterogeneity. BBS is a rare (~1/140,000 to ~1/160,000 in Europe) autosomal recessive pediatric disorder characterized by retinal degeneration, truncal obesity, polydactyly, cognitive impairment, renal dysfunction, and hypogonadism. Twenty-eight genes involved in ciliary structure or function have been implicated in BBS, and explain the molecular basis for ~75%-80% of individuals. To investigate the mutational spectrum of BBS in Romania, we ascertained a cohort of 24 individuals in 23 families. Following informed consent, we performed proband exome sequencing (ES). We detected 17 different putative disease-causing single nucleotide variants or small insertion-deletions and two pathogenic exon disruptive copy number variants in known BBS genes in 17 pedigrees. The most frequently impacted genes were BBS12 (35%), followed by BBS4, BBS7, and BBS10 (9% each) and BBS1, BBS2, and BBS5 (4% each). Homozygous BBS12 p.Arg355* variants were present in seven pedigrees of both Eastern European and Romani origin. Our data show that although the diagnostic rate of BBS in Romania is likely consistent with other worldwide cohorts (74%), we observed a unique distribution of causal BBS genes, including overrepresentation of BBS12 due to a recurrent nonsense variant, that has implications for regional diagnostics.

Biallelic Variants in Seven Different Genes Associated with Clinically Suspected Bardet-Biedl Syndrome.

Bardet-Biedl syndrome (BBS) is a rare clinically and genetically heterogeneous autosomal recessive multi-systemic disorder with 22 known genes. The primary clinical and diagnostic features include six different hallmarks, such as rod-cone dystrophy, learning difficulties, renal abnormalities, male hypogonadism, post-axial polydactyly, and obesity. Here, we report nine consanguineous families and a non-consanguineous family with several affected individuals presenting typical clinical features of BBS. In the present study, 10 BBS Pakistani families were subjected to whole exome sequencing (WES), which revealed novel/recurrent gene variants, including a homozygous nonsense mutation (c.94C>T; p.Gln32Ter) in the IFT27 (NM_006860.5) gene in family A, a homozygous nonsense mutation (c.160A>T; p.Lys54Ter) in the BBIP1 (NM_001195306.1) gene in family B, a homozygous nonsense variant (c.720C>A; p.Cys240Ter) in the WDPCP (NM_015910.7) in family C, a homozygous nonsense variant (c.505A>T; p.Lys169Ter) in the LZTFL1 (NM_020347.4) in family D, pathogenic homozygous 1 bp deletion (c.775delA; p.Thr259Leufs*21) in the MKKS/BBS5 (NM_170784.3) gene in family E, a pathogenic homozygous missense variant (c.1339G>A; p.Ala447Thr) in BBS1 (NM_024649.4) in families F and G, a pathogenic homozygous donor splice site variant (c.951+1G>A; p?) in BBS1 (NM_024649.4) in family H, a pathogenic bi-allelic nonsense variant in MKKS (NM_170784.3) (c.119C>G; p.Ser40*) in family I, and homozygous pathogenic frameshift variants (c.196delA; p.Arg66Glufs*12) in BBS5 (NM_152384.3) in family J. Our findings extend the mutation and phenotypic spectrum of four different types of ciliopathies causing BBS and also support the importance of these genes in the development of multi-systemic human genetic disorders.

Clinical and molecular diagnosis of Bardet-Biedl syndrome (BBS).

Bardet-Biedl syndrome (BBS) is a rare genetic disease of the group of ciliopathies, a group of pathologies characterized mainly by defects in the structure and/or function of primary cilia. The main features of this ciliopathy are retinal dystrophy, obesity, polydactyly, urogenital and renal abnormalities, and cognitive impairment, commonly accompanied by various secondary features, making clear the extensive clinical heterogeneity associated with this syndrome, which, together with the frequent overlapping phenotype with other ciliopathies, greatly complicates its diagnosis. Patients are mainly detected by their pediatrician at quite early ages, usually between 2 and 6years. The pediatrician, given the main symptoms they present, usually refers patients to a specialist. Personalized medicine brought diagnosis closer to many patients who lacked it. It usually presents an autosomal recessive mode of inheritance, but in recent years several authors have proposed more complex inheritance models to explain the frequent inter- and intra-familial clinical variability. The main molecular techniques used for diagnosis are gene panels, the clinical exome and, in certain cases, the patient's complete genome. Although numerous studies have contributed to defining the role of the different BBS genes and designing various strategies for the molecular diagnosis of BBS, as well as delving into the functions performed by these proteins, these advances have not been sufficient to develop a complete treatment for this syndrome. and to be able to offer patients some therapeutic options.

A Case of Laurence Moon Bardet Biedl Syndrome.

INTRODUCTION: Laurence-Moon-Bardet-Biedl syndrome (LMBBS) is a rare autosomal recessive disorder characterised by polydactyly, retinitis pigmentosa, obesity, hypogonadism and mental retardation. MATERIALS: A 20-year old male, who is morbidly obese [BMI = 41] with history of intellectual delay, speech impairment and progressive vision loss. Presented to Saveetha medical college, Chennai with chief complaints of breathlessness, oliguria, abdominal distension. On examination patient had short stature, obese, crowded teeth present, had polydactyly of feet, micro penis and retinitis pigmentosa, nystagmus. He had pedal edema and facial puffiness. Laboratory investigations revealed Hb-6.9, creatinine-12, urea 217, potassium-7.7, bicarbonate-8.3. Echo showed eccentric Left ventricular hypertrophy. CT abdomen revealed hepatomegaly, right contracted kidney with renal pelvic lipomatosis, left enlarged kidney with hydroureteronephrosis grade 4. RESULT: He presented with all the primary Pentad features of LMBBS along with CKD stage 5. He also had secondary features like speech delay, developmental delay, dental crowding, high arched palate, left ventricular hypertrophy. CONCLUSION: LMBBS is a disorder with an identified Pentad of symptoms which are obesity, hypogonadism, intellectual impairment, polydactyly and retinitis pigmentosa. Renal function loss is most common cause of mortality in these patients. Because of seemingly unrelated symptoms the disorder remains largely under diagnosed. Genetic counselling of effected families raise awareness about need to get the other family members assessed for renal and cardiovascular problems. References Khan PA, Nishaat J, Noor S, et al. Laurence Moon Bardet Biedl syndrome: a rare case report in a tertiary care teaching hospital, Hyderabad, Telangana, India. Int J Med Sci Public Health 2017;7(1):68-71. Katsanis N, Lupski JR, Beales PL. Exploring the molecular basis of Bardet-Biedl syndrome. Hum Mol Genet 2001;10(20):2293-2299.

Phenotypic diversity observed in a Chinese patient cohort with biallelic variants in Bardet-Biedl syndrome genes.

PURPOSE: Bardet-Biedl syndrome (BBS) is a rare multisystem ciliopathy. The aim of this study was to describe the clinical and genetic features of a cohort of Chinese patients carrying biallelic BBS gene variants. METHODS: We recruited 34 patients from 31 unrelated pedigrees who carried biallelic pathogenic variants in BBS genes. All patients underwent ophthalmic and systematic evaluations, as well as comprehensive molecular genetic analyses. Ultimately, 14 patients were followed up over time. RESULTS: We identified 47 diseasing-causing variants in 10 BBS genes; 33 were novel. Diagnosis of BBS and non-syndromic retinitis pigmentosa (RP) were established in 28 patients from 27 pedigrees and 6 patients, respectively. The two most prevalent genes in patients with BBS were BBS2 and BBS4, accounting for 51.8% of the probands. The patients exhibited clinical heterogeneity, from patients with all six primary clinical components to patients suffering from non-syndromic RP. The common components were retinal dystrophy, polydactyly, and obesity, with frequencies of 78.6% to 100%, while renal anomaly frequencies were only 7.1%. Patients exhibited early and severe visual defects and retinal degeneration. Patients with biallelic missense variants in BBS2 suffered fewer clinical symptoms and mild visual impairment. Patients with BBS10 variants tended to have cone dystrophy. CONCLUSIONS: Our study defined the mutated gene profiles and established the configuration of the variation frequencies for each BBS gene in Chinese patients. Overall, our patients showed early and severe visual defects and retinal degeneration. Genetic analysis is therefore crucial for diagnosis, genetic counseling, and future gene therapy in these patients.

Bardet-Biedl syndrome associated with novel compound heterozygous variants in BBS12 gene.

BACKGROUND: Bardet-Biedl syndrome (BBS) is a rare autosomal recessive ciliopathy characterized by 6 primary features of rod-cone dystrophy, central obesity, polydactyly, cognitive impairment, hypogonadism and/or genitourinary malformations, and kidney abnormalities. At least 21 genes associated with BBS have been reported. To date, BBS associated with BBS12 variants has never been described in the Japanese population. We report a Japanese infant female with BBS with compound heterozygous BBS12 variants. METHODS: In addition to the pediatric examination, fundus photography, full-field electroretinogram(ffERG) and whole exome sequencing (WES) were underwent. RESULTS: The infant exhibited obesity, polydactyly, cognitive impairment, genitourinary malformations, and kidney dysfunction. At the age of 2 years, ffERG revealed severe reduction in both rod- and cone-mediated electroretinographic responses consistent with a severe form of rod-cone dystrophy, with minimal retinal abnormalities. WES revealed novel compound heterozygous BBS12 variants (c.591T > A, p.Tyr197* and c.1372dupA, p.Thr458Asnfs*5) in the infant. Her parents carried each of the variants, as confirmed by Sanger sequencing. CONCLUSIONS: The current observations will contribute to an expanded understanding of genotype-phenotype associations in BBS12-associated BBS.

Inherited causes of combined vision and hearing loss: clinical features and molecular genetics.

Combined vision and hearing loss, also known as dual sensory impairment, can occur in several genetic conditions, including ciliopathies such as Usher and Bardet-Biedl syndrome, mitochondrial DNA disorders and systemic diseases, such as CHARGE, Stickler, Waardenburg, Alport and Alstrom syndrome. The retinal phenotype may point to the diagnosis of such disorders. Herein, we aim to provide a comprehensive review of the molecular genetics and clinical features of the most common non-chromosomal inherited disorders to cause dual sensory impairment.

A Japanese boy with Bardet-Biedl syndrome caused by a novel homozygous variant in the ARL6 gene who was initially diagnosed with retinitis punctata albescens: A case report.

PURPOSE: Bardet-Biedl Syndrome (BBS) is an autosomal recessive systemic disorder characterized by retinitis pigmentosa, polydactyly, obesity, intellectual disability, renal impairments, and hypogonadism. The purpose of this study was to determine the ocular characteristics of a boy with BBS caused by a novel homozygous variant in the ARL6 (alternative named BBS3) gene who had been originally diagnosed with retinitis punctata albescens. METHODS: This was an observational case study. The patient underwent ophthalmological examinations, electroretinography, and genetic analyses using whole-exome sequencing. RESULTS: A 7-year-old boy was examined in our hospital with complaints of a progressive reduction of his visual acuity and night blindness in both eyes. There was no family history of eye diseases and no consanguineous marriage. Fundus examinations showed numerous white spots in the deep retina and retinal pigment epithelium. Fundus autofluorescence showed hypofluorescence consistent with these spots. Both the scotopic and photopic components of the full-field electroretinographies were non-detectable. Based on these clinical findings, this boy was suspected to have retinitis punctata albescens. Subsequent genetic testing using whole-exome sequencing revealed a novel homozygous variants in the ARL6/BBS3 gene (NM_001278293.3:c.528G>A, (p.Trp176Ter)). A systemic examination by the pediatric department revealed that this boy had a history of a surgical excision of polydactyly on his left foot when he was born, and that he was mildly obese. There were no prominent intellectual or gonadal dysfunctions, no craniofacial or dental abnormalities, no congenital heart disease, and no hearing impairment. He was then clinically and genetically diagnosed with BBS. CONCLUSION AND IMPORTANCE: In children with night blindness and progressive visual dysfunction, it is important for ophthalmologists to consult clinical geneticists and pediatricians to rule out the possibility of systemic diseases such as BBS.

Síndrome de Bardet Biedl: a propósito de un caso / Bardet Biedl syndrome: a case report

El síndrome de Bardet Biedl es un síndrome genético de herencia autosómica recesiva con compromiso multisistémico y gran variabilidad en su presentación clínica; son características la obesidad, la polidactilia, el hipogonadismo y las alteraciones renales, visuales y cognitivas. Pertenece a las llamadas ciliopatías. El diagnóstico es clínico y puede ser confirmado por estudios genéticos. No existe un tratamiento específico de la patología; se requiere un abordaje multidisciplinario. Se presenta el caso de una paciente de 13 años con obesidad e hiperfagia, diabetes tipo 2, hipotiroidismo, polidactilia, alteraciones del aprendizaje y alteraciones visuales. Se le realizó un panel genético para obesidad en el que se detectaron dos variantes heterocigotas patológicas en el gen BBS2.

Bardet Biedl syndrome is an autosomal recessive ciliopathie. It is a pleiotropic disorder characterised by retinal dystrophy, renal dysfunction, polydactyly, obesity, cognitive deficitand hypogenitalism. Diagnosis is based on clinical features. Molecular genetic testing is available. There is no specific treatment, a multidisciplinary approach is required. We report the case of a 13-year-old female patient with obesity and hyperphagia, type 2 diabetes, hypothyroidism, polydactyly,cognitive deficit and visual impairment. A multigenic panel allowed the identification of two heterozygous pathogenic variants in the BBS2 gene.

[Bardet Biedl syndrome: a case report]. / Síndrome de Bardet Biedl: a propósito de un caso.

Bardet Biedl syndrome is an autosomal recessive ciliopathie. It is a pleiotropic disorder characterised by retinal dystrophy, renal dysfunction, polydactyly, obesity, cognitive deficit and hypogenitalism. Diagnosis is based on clinical features. Molecular genetic testing is available. There is no specific treatment, a multidisciplinary approach is required. We report the case of a 13-year-old female patient with obesity and hyperphagia, type 2 diabetes, hypothyroidism, polydactyly, cognitive deficit and visual impairment. A multigenic panel allowed the identification of two heterozygous pathogenic variants in the BBS2 gene.

El síndrome de Bardet Biedl es un síndrome genético de herencia autosómica recesiva con compromiso multisistémico y gran variabilidad en su presentación clínica; son características la obesidad, la polidactilia, el hipogonadismo y las alteraciones renales, visuales y cognitivas. Pertenece a las llamadas ciliopatías. El diagnóstico es clínico y puede ser confirmado por estudios genéticos. No existe un tratamiento específico de la patología; se requiere un abordaje multidisciplinario. Se presenta el caso de una paciente de 13 años con obesidad e hiperfagia, diabetes tipo 2, hipotiroidismo, polidactilia, alteraciones del aprendizaje y alteraciones visuales. Se le realizó un panel genético para obesidad en el que se detectaron dos variantes heterocigotas patológicas en el gen BBS2.

Diagnosis and genetic analysis of a case with Bardet-Biedl syndrome caused by compound heterozygous mutations in the BBS12 gene.

Bardet-Biedl syndrome (BBS) is a rare autosomal recessive ciliopathy, which is caused by mutations mainly in genes encoding BBSome complex and IFT complex. Here, we reported a 21-year-old female with BBS characterized by three primary features including obesity, retinitis pigmentosa sine pigmento and bilateral renal cysts. She also had some secondary features such as diabetes mellitus, nonalcoholic fatty liver disease, subclinical hypothyroidism and mild conductive hearing damage. Whole exome sequencing revealed two compound heterozygous mutations in exon 2 of the BBS12 gene (c.188delC, p.T63fs and c.1993_1995del, p.665_665del) in this patient. Sanger sequencing showed that her father and mother carried c.188delC (p.T63fs) and c.1993_1995del (p.665_665del) variants, respectively, while her parents were free of BBS-related symptoms. In conclusion, this case reported two novel mutations (c.188delC, p.T63fs and c.1993_1995del, p.665_665del) of the BBS12 gene in a girl presented with BBS, which provides novel genetic resources for studies of the disease. Meanwhile, the BBS case shows the entire development progress from her birth to adulthood, which helps facilitate clinicians' understanding of BBS.