Cilia get serious: Meckel–Gruber and Bardet–Biedl syndromes represent a spectrum of allelic disorders

Hypomorphic mutations in syndromic encephalocele genes are associated with Bardet-Biedl syndrome
Leitch et al. (2008)
Nature Genetics 40: 443–448     

Idiopathic rhinitis, the ongoing quest

The term rhinitis in daily practice is used for nasal dysfunction causing symptoms-like nasal itching, sneezing, rhinorrhea and or nasal blockage. Chronic rhinitis can roughly be classified into allergic, infectious or nonallergic/noninfectious. When allergy, mechanical obstruction and infections have been excluded as the cause of rhinitis, a number of poorly defined nasal conditions of partly unknown aetiology and pathophysiology remain. The differential diagnosis of nonallergic noninfectious rhinitis is extensive. Although the percentage of patients with nonallergic noninfectious rhinitis with a known cause has increased the last decades, still about 50% of the patients with nonallergic noninfectious rhinitis has to be classified as suffering from idiopathic rhinitis (IR), or rather e causa ignota. Specific immunological, clinical and sometimes radiological and functional tests are required to distinguish known causes. Research to the underlying pathophysiology of IR has moved from autonomic neural dysbalans to inflammatory disorders (local allergy), the nonadrenergic noncholinergic (NANC) sensory peptidergic neural system and central neural hyperaesthesia, still without solid ground or proof. This review summarizes the currently known causes for nonallergic noninfectious rhinitis and possible treatments. Also possible pathophysiological mechanisms of IR are discussed.     

Phenotypic overlap of McKusick‐Kaufman syndrome with Bardet‐Biedl syndrome: A literature review

Hydrometrocolpos (HMC) and post‐axial polydactyly (PAP) are common to both McKusick‐Kaufman syndrome (MKS) and Bardet‐Biedl syndrome (BBS). We review reported cases of MKS and BBS presenting with HMC and PAP early in life to determine if there are clinical features that allow discrimination between the two syndromes as the primary features of retinitis pigmentosa, obesity, learning disability in BBS are age‐dependent. We did not find any phenotypic features that allowed reliable differentiation between the two syndromes in the neonatal period. However, uterine, ovarian, and fallopian tube anomalies are more common in BBS patients, and it may be that these clinical features prove to be useful discriminating features. We conclude that sporadic female infants with HMC and PAP cannot be diagnosed with MKS until at least age 5 years and that monitoring for the complications of BBS should be performed in these patients. Am. J. Med. Genet. 95:208–215, 2000. Published 2000 Wiley‐Liss, Inc.     

Potential amelioration of morbidity in patients with chromosomal anomalies: relevance to Bardet‐Biedl syndrome

Genuis SJ, Lobo RA. Potential amelioration of morbidity in patients with chromosomal anomalies: relevance to Bardet‐Biedl syndrome. Given the genetic basis of their disease, children with major chromosomal abnormalities including Bardet–Biedl syndrome (BBS) are generally considered to have a guarded prognosis with persistence or progression of disease manifestations. Although various therapeutic interventions are commonly used to control signs and symptoms of illness, parents of BBS children are usually cautioned against hoping for sustained improvement. A case of a 21‐month‐old girl, diagnosed with BBS, manifesting signs of worsening visual impairment, obesity, irascible and disordered behaviour, as well as developmental delay, is presented. After initial evaluation suggested specific biochemical deficiencies, nutritional status correction was undertaken and the patient's signs and symptoms subsequently resolved over the course of several months. To the authors' knowledge, this is the first case report of sustained resolution of all disease manifestations in the face of previously deteriorating health in a young child with this major chromosomal abnormality. It appears that biochemical imbalances and insufficiencies resulting from abnormal metabolism and excretion are potentially amenable to extraordinary dietary supplementation, with partial or complete resolution of clinical abnormalities. It is recommended that all children with chromosomal abnormalities have biochemical and nutritional status evaluation with correction of disordered biochemistry as is possible.     

Genetic predictors of cardiovascular morbidity in Bardet–Biedl syndrome

Bardet–Biedl syndrome is a rare ciliopathy characterized by retinal dystrophy, obesity, intellectual disability, polydactyly, hypogonadism and renal impairment. Patients are at high risk of cardiovascular disease. Mutations in BBS1 and BBS10 account for more than half of those with molecular confirmation of the diagnosis. To elucidate genotype–phenotype correlations with respect to cardiovascular risk indicators 50 patients with mutations in BBS1 were compared with 19 patients harbouring BBS10 mutations. All patients had truncating, missense or compound missense/truncating mutations. The effect of genotype and mutation type was analysed. C‐reactive protein was higher in those with mutations in BBS10 and homozygous truncating mutations (p = 0.013 and p = 0.002, respectively). Patients with mutations in BBS10 had higher levels of C peptide than those with mutations in BBS1 (p = 0.043). Triglyceride levels were significantly elevated in patients with homozygous truncating mutations (p = 0.048). Gamma glutamyl transferase was higher in patients with homozygous truncating mutations (p = 0.007) and heterozygous missense and truncating mutations (p = 0.002) than those with homozygous missense mutations. The results are compared with clinical cardiovascular risk factors. Patients with missense mutations in BBS1 have lower biochemical cardiovascular disease markers compared with patients with BBS10 and other BBS1 mutations. This could contribute to stratification of the clinical service.     

Olfaction evaluation and correlation with brain atrophy in Bardet‐Biedl syndrome

Bardet‐Biedl syndrome (BBS) is a well‐recognized ciliopathy characterized by cardinal features namely: early onset retinitis pigmentosa, polydactyly, obesity, hypogonadism, renal and cognitive impairment. Recently, disorders of olfaction (anosmia, hyposmia) have been also described in BBS patients. Moreover, morphological brain anomalies have been reported and prompt for further investigations to determine whether they are primary or secondary to peripheral organ involvement (i.e. visual or olfactory neuronal tissue). The objective of this article is to evaluate olfactory disorders in BBS patients and to investigate putative correlation with morphological cerebral anomalies. To this end, 20 BBS patients were recruited and evaluated for olfaction using the University of Pennsylvania Smell Identification Test (UPSIT). All of them underwent a structural magnetic resonance imaging (MRI) scan. We first investigated brain morphological differences between BBS subjects and 14 healthy volunteers. Then, we showed objective olfaction disorders in BBS patients and highlight correlation between gray matter volume reduction and olfaction dysfunction in several brain areas.     

Exploiting worm and allergy models to understand Th2 cytokine biology

PURPOSE OF REVIEW: Helminthic parasites and many allergens trigger highly polarized Th2-type immune responses. In most helminth infections, the Th2 response often leads to parasite expulsion or sequestration. During murine Schistosoma mansoni infection, however, the parasites persist and the chronic Th2 response induces severe pathological changes in the gut and liver. Thus, the study of schistosome infections in mice has become a popular model to study the pathogenesis of Th2 cytokine-mediated disease. This review will discuss recent findings from the schistosomiasis model that may be relevant to the understanding of allergic inflammation, asthma and Th2 cytokine biology in general. RECENT FINDINGS: Evidence is accumulating that the Th2 pathway is not a 'default pathway' but one that is actively instructed by mechanisms that are only beginning to be understood. Other areas of intensive investigation include studies on alternatively activated macrophages, the role of dendritic cells in Th2 response development, the inhibitory function of IL-10, regulatory T-cells and decoy receptors on chronic Th2-mediated inflammation, and the role of chitinases in mediating Th2 disease. Finally, the development of novel eosinophil-deficient mice has also accelerated our understanding of the contribution of this important cell type to Th2 immunity. SUMMARY: Many findings from the schistosomiasis model have been subsequently demonstrated in models of allergic disease, illustrating the utility of this model to dissect basic mechanisms of Th2-mediated inflammation. Further study of helminth-induced Th2 responses may expedite the discovery of new therapeutics for a wide range of Th2-associated diseases.     

Bardet‐Biedl syndrome in Denmark—report of 13 novel sequence variations in six genes

Bardet‐Biedl syndrome (BBS) is an autosomal recessive disease characterized by retinal dystrophy, polydactyly, obesity, learning disabilities, renal involvement, and male hypogenitalism. BBS is genetically heterogeneous with mutations of 14 genes, accounting for approximately 70% of cases. Triallelic inheritance has been suggested in about 5% of cases. Forty‐nine unrelated BBS patients were screened for mutations by DHPLC analysis in BBS1, BBS2, BBS4, BBS6/MKKS, BBS10, and BBS12. The selected genes either account for more than 5% of the mutational load or are commonly reported in triallelic inheritance. Eight patients with only one or no BBS mutation were further investigated by single nucleotide polymorphism (SNP) analysis. In total, mutations were detected in 44 patients. Twenty percent had two mutations in BBS1, 18% in BBS2, 4% in BBS9, 43% in BBS10, and 2% in BBS12. Five patients were heterozygous for a sequence variation in BBS6/MKKS. We found eight patients with three sequence variations in two genes, which could be explained by triallelic inheritance, by the prevalence of heterozygous carriers or the third sequence variations representing rare polymorphisms. All changes found in a second BBS gene were amino acid substitutions. Genotype–phenotype correlations suggest a milder phenotype for BBS1 compared to BBS2 and BBS10, which we ascribe to the hypomorphic p.Met390Arg‐mutation. Hum Mutat 31:429–436, 2010. © 2010 Wiley‐Liss, Inc.     

Bardet‐Biedl syndrome type 3 in an Iranian family: Clinical study and confirmation of disease localization

Bardet‐Biedl syndrome (BBS) is a group of autosomal recessive MCA/MR syndromes characterized by pigmentary retinopathy, postaxial polydactyly, hypogenitalism, obesity, and mental retardation. Five BBS loci have been identified; among them, BBS type 1 (BBS1) and type 3 (BBS3) are most common and most rare, respectively. We encountered an Iranian family that had seven affected members. All patients had a history of mild to severe obesity, but it was reversible in some patients by caloric restriction and exercise. All patients had pigmentary retinopathy, beginning as night blindness in early childhood and progressing toward severe impairment of vision by the end of the second decade. Polydactyly varied in limb distribution, ranging from four‐limb involvement to random involvement or even to nonaffectedness. Six of the seven patients were not mentally retarded. Although kidney anomaly or an adrenal mass was pres‐ ent in two patients, the fact that one patient had seven children rules out reproductive dysfunction. Linkage analysis with microsatellite markers showed that the disease in the family was assigned to a region around marker loci at 3p13‐p12 (maximum LOD score = 4.15 and recombination fraction θ = 0, at D3S1603 microsatellite marker), to which the BBS3 locus has been mapped. Haplotype analysis did not reduce the extent of the previously reported critical region of BBS3. A comparison of clinical manifestations of our patients with those of previously reported BBS3 patients did not support any type‐specific phenotypes, though manifestations in our patients are similar to those in BBS3 patients of a family in Newfoundland. Am. J. Med. Genet. 94:433–437, 2000. © 2000 Wiley‐Liss, Inc.     

Value of MRI olfactory bulb evaluation in the assessment of olfactory dysfunction in Bardet–Biedl syndrome

Olfactory bulb (OB) volume evaluation by magnetic resonance imaging (MRI) has been demonstrated to be related to olfactory dysfunction in many different diseases. Olfactory dysfunction is often overlooked in Bardet?Biedl syndrome (BBS) patients and is rarely objectively evaluated by MRI. We present a series of 20 BBS patients with olfactory dysfunction. The OB was evaluated separately and blindly by two radiologists (SR and SM) with 3 Tesla MRI imaging comparatively to 12 normal control subjects by global visual evaluation and by quantitative measurement of OB volume. In the 12 control cases OB visual evaluation was considered as normal in all cases for radiologist (SR) and in 10 cases for radiologist (SM). In the 20 BBS patients, OB visual evaluation was considered as abnormal in 18 cases for SR and in all cases for SM. OB volumetric evaluation for SR and SM in BBS patients was able to provide significant correlation between BBS and olfactory dysfunction. This study indicates that OB volume evaluation by MRI imaging like structural MRI scan for gray matter modifications demonstrates that olfactory dysfunction in BBS patients is a constant and cardinal symptom integrated in a genetical syndrome with peripheral and central olfactory structure alterations.     

Combining fetal sonography with genetic and allele pathogenicity studies to secure a neonatal diagnosis of Bardet–Biedl syndrome

Bardet–Biedl syndrome (BBS) is a rare pediatric ciliopathy characterized by marked clinical variability and extensive genetic heterogeneity. Typical diagnosis of BBS is secured at a median of 9 years of age, and sometimes well into adolescence. Here, we report a patient in whom prenatal detection of increased nuchal fold, enlarged echogenic kidneys, and polydactyly prompted us to screen the most commonly mutated genes in BBS and the phenotypically and genetically overlapping ciliopathy, Meckel–Gruber syndrome (MKS). We identified the common Met390Arg mutation in BBS1 in compound heterozygosity with a novel intronic variant of unknown significance (VUS). Testing of mRNA harvested from primary foreskin fibroblasts obtained shortly after birth revealed the VUS to induce a cryptic splice site, which in turn led to a premature termination and mRNA degradation. To our knowledge, this is the earliest diagnosis of BBS in the absence of other affected individuals in the family, and exemplifies how combining clinical assessment with genetic and timely assays of variant pathogenicity can inform clinical diagnosis and assist with patient management in the prenatal and neonatal setting.     

Exploration of the cognitive,adaptive and behavioral functioning of patients affected with Bardet–Biedl syndrome

The aim of the study was to investigate the behavioral phenotype of patients affected with Bardet–Biedl syndrome (BBS). Twenty‐four patients with molecularly confirmed diagnosis of BBS (6–38 years old) were evaluated using standardized neuropsychological tests. Results were compared with normative data. The mean intellectual functioning of participants fell 1.5 standard deviations below normal expectations; though, the majority of participants (75–80%) did not display an intellectual disability. The group's mean performance on most cognitive tasks and all scales of adaptive functioning was significantly weaker than norms. The majority (55–60%) of participants displayed broadly average verbal fluency and auditory rote learning, while 22–40% were severely impaired in the same areas. The majority of participants were severely impaired in perceptual reasoning (53%), attentional capacity (69%), and functional independence (74%). Symptoms associated with Autism were reported for 77% of participants. Behavioral issues were unrelated to intellectual ability but significantly correlated with adaptive functioning. This first neurocognitive evaluation of a molecularly confirmed cohort of BBS patients shows that the majority of patients experience significant difficulties with perceptual intellectual abilities, auditory attentional capacity, adaptive independence, and behavior. The frequency of autism‐related symptoms far exceeds the incidence rate of diagnosed autism in general and warrants further investigations.     

Clinical and genetic characterization of Bardet–Biedl syndrome in Tunisia: defining a strategy for molecular diagnosis

Bardet–Biedl syndrome (BBS, OMIM 209900) is a rare genetic disorder characterized by obesity, retinitis pigmentosa, post axial polydactyly, cognitive impairment, renal anomalies and hypogonadism. The aim of this study is to provide a comprehensive clinical and molecular analysis of a cohort of 11 Tunisian BBS consanguineous families in order to give insight into clinical and genetic spectrum and the genotype–phenotype correlations. Molecular analysis using combined sequence capture and high‐throughput sequencing of 30 ciliopathies genes revealed 11 mutations in 11 studied families. Five mutations were novel and six were previously described. Novel mutations included c.1110G>A and c.39delA (p.G13fs*41) in BBS1, c.115+5G>A in BBS2, c.1272+1G>A in BBS6, c.1181_1182insGCATTTATACC in BBS10 (p.S396Lfs*6). Described mutations included c.436C>T (p.R146*) and c.1473+4A>G in BBS1, c.565C> (p.R189*) in BBS2, deletion of exons 4–6 in BBS4, c.149T>G (p.L50R) in BBS5, and c.459+1G>A in BBS8; most frequent mutations were described in BBS1 (4/11, 37%) and BBS2 (2/11, 18%) genes. No phenotype–genotype correlation was evidenced. This data expands the mutations profile of BBS genes in Tunisia and suggests a divergence of the genetic spectrum comparing Tunisian and other populations.