A patient with peripheral demyelinating neuropathy,central dysmyelinating leukodystrophy,Waardenburg syndrome,and severe hypoganglionosis associated with a novel SOX10 mutation

In this report, we present the case of a female infant with peripheral demyelinating neuropathy, central dysmyelinating leukodystrophy, Waardenburg syndrome, and Hirschsprung disease (PCWH) associated with a novel frameshift mutation (c.842dupT) in exon 5, the last exon of SOX10. She had severe hypoganglionosis in the small intestine and entire colon, and suffered from frequent enterocolitis. The persistence of ganglion cells made both the diagnosis and treatment difficult in the neonatal period. She also showed hypopigmentation of the irises, hair and skin, bilateral sensorineural deafness with hypoplastic inner year, severe demyelinating neuropathy with hypotonia, and diffuse brain hypomyelination. The p.Ser282GlnfsTer12 mutation presumably escapes from nonsense‐mediated decay and may generate a dominant‐negative effect. We suggest that hypoganglionosis can be a variant intestinal manifestation associated with PCWH and that hypoganglionosis and aganglionosis may share the same pathoetiological mechanism mediated by SOX10 mutations.     

Anticipation in a unique family with Charcot‐Marie‐Tooth syndrome and deafness: Delineation of the clinical features and review of the literature

Charcot‐Marie‐Tooth disease (CMT) is a clinically and genetically heterogeneous group of polyneuropathies characterized by degeneration of peripheral nerves, resulting in distal muscle atrophy, sensory loss, and deformities of hands and feet. We have studied 34 individuals in a large 84‐member four‐generation central Illinois family with autosomal dominant Charcot‐Marie‐Tooth and deafness. Nerve conduction velocities are consistent with type 1 CMT. Audiological evaluation revealed both auditory neuropathy and cochlear involvement in affected individuals. There is increasing clinical severity and younger age of onset of CMT and deafness with each progressive generation, suggestive of anticipation (P < 0.05). The proband, a female diagnosed at birth with hypotonia, bilateral vocal cord palsy, swallowing incoordination, and hearing impairment, died at age 18 months. Another individual died at the age of 3 months from hypotonia later attributed to CMT. Genetic analysis indicated that affected individuals in this family do not have the common 1.4 Mb duplication associated with type 1A CMT; however, all affected individuals have a unique G to C transversion at position 248 in coding exon 3 of the peripheral myelin PMP22 gene located on chromosome 17p11.2‐p12. This mutation is predicted to cause an Ala67Pro substitution in the second transmembrane domain of PMP22, consistent with the molecular cause of the CMT phenotype. However, it does not explain the cochlear component of the deafness, the clinical observation of anticipation, and other features in this family. © 2002 Wiley‐Liss, Inc.     

Tietz syndrome (hypopigmentation/deafness) caused by mutation of MITF

Patients with Tietz syndrome have congenital profound deafness and generalised hypopigmentation, inherited in a fully penetrant autosomal dominant fashion. The pigmentary features and complete penetrance make this syndrome distinct among syndromes with pigmentary anomalies and deafness, which characteristically have patchy depigmentation and variable penetrance. Only one family has been reported with the exact features described in the original report of this syndrome. This family was reascertained and a missense mutation was found in the basic region of the MITF gene in family members with Tietz syndrome. Mutations in other regions of this gene have been found to produce Waardenburg syndrome type 2 (WS2), which also includes pigmentary changes and hearing loss, but in contrast to Tietz syndrome, depigmentation is patchy and hearing loss is variable in WS2.


Keywords: Tietz syndrome; Waardenburg syndrome; deafness; MITF     

Piebaldism with deafness: Molecular evidence for an expanded syndrome

In a South African girl of Xhosa stock with severe piebaldism and profound congenital sensorineural deafness we identified a novel missense substitution at a highly conserved residue in the intracellular kinase domain of the KIT proto-oncogene, R796G. Though auditory anomalies have been observed in mice with dominant white spotting (W) due to KIT mutations, deafness is not typical in human piebaldism. Thus, the occurrence of sensorineural deafness in this patient extends considerably the phenotypic range of piebaldism due to KIT gene mutation in humans and tightens the clinical similarity between piebaldism and the various forms of Waardenburg syndrome. Am. J. Med. Genet. 75:101–103, 1998. © 1998 Wiley-Liss, Inc.     

Analysis of variability of clinical manifestations in Waardenburg syndrome

Expression of clinical findings of Waardenburg syndrome type 1 (WS1) and type 2 (WS2) is extremely variable. Using our collection of 26 WS1 and 8 WS2 families, we analyzed the occurrence, severity, and symmetry of clinical manifestations associated with WS. We found significant differences between WS1 and WS2 in deafness, and in pigmentary and craniofacial anomalies. Factor analysis was used to identify manifestations which covaried, resulting in 2 orthogonal factors. Since mean factor scores were found to differ when compared between WS1 and WS2, we suggest that these factors could be useful in distinguishing WS types. We found that the WS gene was transmitted from mothers more often than from fathers. We also extensively examined the W-Index, a continuous measure of dystopia canthorum. Our data suggest that use of the W-Index to discriminate between affected WS1 and WS2 individuals may be problematic since 1) ranges of W-Index scores of affected and unaffected individuals over-lapped considerably within both WS1 and WS2, and 2) a considerable number of both affected and unaffected WS2 individuals exhibited W-index scores consistent with dystopia canthorum. Misclassification of families may have implications for risk assessment of deafness, since WS2 families have been reported to have greater incidence of deafness, as confirmed in our study. © 1995 Wiley-Liss, Inc.     

SOX10 mutations mimic isolated hearing loss

Ninety genes have been identified to date that are involved in non‐syndromic hearing loss, and more than 300 different forms of syndromic hearing impairment have been described. Mutations in SOX10, one of the genes contributing to syndromic hearing loss, induce a large range of phenotypes, including several subtypes of Waardenburg syndrome and Kallmann syndrome with deafness. In addition, rare mutations have been identified in patients with isolated signs of these diseases. We used the recent characterization of temporal bone imaging aspects in patients with SOX10 mutations to identify possible patients with isolated hearing loss due to SOX10 mutation. We selected 21 patients with isolated deafness and temporal bone morphological defects for mutational screening. We identified two SOX10 mutations and found that both resulted in a non‐functional protein in vitro. Re‐evaluation of the two affected patients showed that both had previously undiagnosed olfactory defects. Diagnosis of anosmia or hyposmia in young children is challenging, and particularly in the absence of magnetic resonance imaging (MRI), SOX10 mutations can mimic non‐syndromic hearing impairment. MRI should complete temporal bones computed tomographic scan in the management of congenital deafness as it can detect brain anomalies, cochlear nerve defects, and olfactory bulb malformation in addition to inner ear malformations.     

Schimke XLID syndrome results from a deletion in BCAP31

A family with three affected males and a second family with a single affected male with intellectual disability, microcephaly, ophthalmoplegia, deafness, and Involuntary limb movements were reported by Schimke and Associates in 1984. The affected males with Schimke X‐linked intellectual disability (XLID) syndrome (OMIM# 312840) had a similar facial appearance with deep‐set eyes, downslanting palpebral fissures, hypotelorism, narrow nose and alae nasi, cupped ears and spacing of the teeth. Two mothers had mild hearing loss but no other manifestations of the disorder. The authors considered the disorder to be distinctive and likely X‐linked. Whole genome sequencing in the single affected male available and the three carrier females from one of the families with Schimke XLID syndrome identified a 2 bp deletion in the BCAP31 gene. During the past decade, pathogenic alterations of the BCAP31 gene have been associated with deafness, dystonia, and central hypomyelination, an XLID condition given the eponym DDCH syndrome. A comparison of clinical findings in Schimke XLID syndrome and DDCH syndrome shows them to be the same clinical entity. The BCAP31 protein functions in endoplasmic reticulum‐associated degradation to promote ubiquitination and destruction of misfolded proteins.     

Performance of cochlear implant recipients with GJB2‐related deafness

Congenital profound hearing loss affects 0.05–0.1% of children and has many causes, some of which are associated with cognitive delay. For prelingually‐deafened cochlear implant recipients, the etiology of deafness is usually unknown. Mutations in GJB2 have been established as the most common cause of heritable deafness in the United States. In this report, we identify cochlear implant recipients with GJB2‐related deafness and examine the performance of these individuals. Cochlear implant recipients received a battery of perceptive, cognitive, and reading tests. Neither subjects nor examiners knew the etiology of deafness in these individuals. The implant recipients were then examined for mutations in GJB2 using an allele‐specific polymerase chain reaction assay, single‐strand conformation polymorphism analysis, and direct sequencing. GJB2 mutations were the leading cause of congenital deafness among the cochlear implant recipients screened. Cochlear implant recipients with GJB2‐related deafness read within one standard deviation of hearing controls better than other congenitally deaf cochlear implant recipients and non‐cochlear implant recipients. Individuals with congenital deafness should be offered GJB2 screening. Positive results establish an etiologic diagnosis and provide prognostic, genetic, and therapeutic information. Effective rehabilitation for profoundly deaf individuals with GJB2‐related deafness is possible through cochlear implantation. © 2002 Wiley‐Liss, Inc.     

The expanding LARS2 phenotypic spectrum: HLASA,Perrault syndrome with leukodystrophy,and mitochondrial myopathy

LARS2 variants are associated with Perrault syndrome, characterized by premature ovarian failure and hearing loss, and with an infantile lethal multisystem disorder: Hydrops, lactic acidosis, sideroblastic anemia (HLASA) in one individual. Recently we reported LARS2 deafness with (ovario) leukodystrophy. Here we describe five patients with a range of phenotypes, in whom we identified biallelic LARS2 variants: three patients with a HLASA‐like phenotype, an individual with Perrault syndrome whose affected siblings also had leukodystrophy, and an individual with a reversible mitochondrial myopathy, lactic acidosis, and developmental delay. Three HLASA cases from two unrelated families were identified. All were males with genital anomalies. Two survived multisystem disease in the neonatal period; both have developmental delay and hearing loss. A 55‐year old male with deafness has not displayed neurological symptoms while his female siblings with Perrault syndrome developed leukodystrophy and died in their 30s. Analysis of muscle from a child with a reversible myopathy showed reduced LARS2 and mitochondrial complex I levels, and an unusual form of degeneration. Analysis of recombinant LARS2 variant proteins showed they had reduced aminoacylation efficiency, with HLASA‐associated variants having the most severe effect. A broad phenotypic spectrum should be considered in association with LARS2 variants.     

The incidence of deafness is non-randomly distributed among families segregating for Waardenburg syndrome type 1 (WS1).

Waardenburg syndrome (WS) is caused by autosomal dominant mutations, and is characterised by pigmentary anomalies and various defects of neural crest derived tissues. It accounts for over 2% of congenital deafness. WS shows high variability in expressivity within families and differences in penetrance of clinical traits between families. While mutations in the gene PAX3 seem to be responsible for most, if not all, WS type 1, it is still not clear what accounts for the reduced penetrance of deafness. Stochastic events during development may be the factors that determine whether a person with a PAX3 mutation will be congenitally deaf or not. Alternatively, genetic background or non-random environmental factors or both may be significant. We compared the likelihoods for deafness in affected subjects from 24 families with reported PAX3 mutations, and in seven of the families originally described by Waardenburg. We found evidence that stochastic variation alone does not explain the differences in penetrances of deafness among WS families. Our analyses suggest that genetic background in combination with certain PAX3 alleles may be important factors in the aetiology of deafness in WS.     

Mutational and phenotypic spectra of KCNE1 deficiency in Jervell and Lange‐Nielsen Syndrome and Romano‐Ward Syndrome

KCNE1 encodes a regulatory subunit of the KCNQ1 potassium channel‐complex. Both KCNE1 and KCNQ1 are necessary for normal hearing and cardiac ventricular repolarization. Recessive variants in these genes are associated with Jervell and Lange‐Nielson syndrome (JLNS1 and JLNS2), a cardio‐auditory syndrome characterized by congenital profound sensorineural deafness and a prolonged QT interval that can cause ventricular arrhythmias and sudden cardiac death. Some normal‐hearing carriers of heterozygous missense variants of KCNE1 and KCNQ1 have prolonged QT intervals, a dominantly inherited phenotype designated Romano‐Ward syndrome (RWS), which is also associated with arrhythmias and elevated risk of sudden death. Coassembly of certain mutant KCNE1 monomers with wild‐type KCNQ1 subunits results in RWS by a dominant negative mechanism. This paper reviews variants of KCNE1 and their associated phenotypes, including biallelic truncating null variants of KCNE1 that have not been previously reported. We describe three homozygous nonsense mutations of KCNE1 segregating in families ascertained ostensibly for nonsyndromic deafness: c.50G>A (p.Trp17*), c.51G>A (p.Trp17*), and c.138C>A (p.Tyr46*). Some individuals carrying missense variants of KCNE1 have RWS. However, heterozygotes for loss‐of‐function variants of KCNE1 may have normal QT intervals while biallelic null alleles are associated with JLNS2, indicating a complex genotype‐phenotype spectrum for KCNE1 variants.     

Power and Related Statistical Properties of Conditional Likelihood Score Tests for Association Studies in Nuclear Families with Parental Genotypes

Both population based and family based case control studies are used to test whether particular genotypes are associated with disease. While population based studies have more power, cryptic population stratification can produce false‐positive results. Family‐based methods have been introduced to control for this problem. This paper presents the full likelihood function for family‐based association studies for nuclear families ascertained on the basis of their number of affected and unaffected children. The likelihood of a family factors into the probability of parental mating type, conditional on offspring phenotypes, times the probability of offspring genotypes given their phenotypes and the parental mating type. The first factor can be influenced by population stratification, whereas the latter factor, called the conditional likelihood, is not. The conditional likelihood is used to obtain score tests with proper size in the presence of population stratification (see also Clayton (1999) and Whittemore & Tu (2000) ). Under either the additive or multiplicative model, the TDT is known to be the optimal score test when the family has only one affected child. Thus, the class of score tests explored can be considered as a general family of TDT‐like procedures. The relative informativeness of the various mating types is assessed using the Fisher information, which depends on the number of affected and unaffected offspring and the penetrances. When the additive model is true, families with parental mating type Aa×Aa are most informative. Under the dominant (recessive) model, however, a family with mating type Aa×aa (AA×Aa) is more informative than a family with doubly heterozygous (Aa×Aa) parents. Because we derive explicit formulae for all components of the likelihood, we are able to present tables giving required sample sizes for dominant, additive and recessive inheritance models.     

Clinical features,molecular results,and management of 12 individuals with the rare arthrochalasia Ehlers‐Danlos syndrome

Arthrochalasia Ehlers‐Danlos syndrome (aEDS) is a rare autosomal dominant connective tissue disorder that is characterized by congenital bilateral hip dislocations, severe generalized joint hypermobility, recurrent joint (sub)luxations, and skin hyperextensibility. To date, 42 patients with aEDS have been published. We report 12 patients with aEDS from 10 families with 6 unpublished individuals and follow‐up data on 6 adult patients. The clinical features are largely comparable with patients reported in the literature. Most (n = 10) patients had variants leading to (partial) loss of exon 6 of the COL1A1 or COL1A2 genes. One patient did not have a previously reported likely pathogenic COL1A1 variant. Data regarding management were retrieved. Hip surgery was performed in 5/12 patients and 3/12 patients underwent spinal surgery. As much as 4/12 patients were wheelchair‐bound or unable to walk unaided. Fractures were present in 9/12 individuals with 1 patient requiring bisphosphonate treatment. Echocardiograms were performed in 10 patients and 2 individuals showed an abnormality likely unrelated to aEDS. One patient gave birth to two affected children and went through preterm labor requiring medication but had no additional complications. Of the eight adults in our cohort, the majority entered a career. Our data point toward a genotype–phenotype relationship with individuals with aEDS due to pathogenic COL1A1 variants causing complete or partial loss of exon 6 being more severely affected regarding musculoskeletal features. There is a significant lack of knowledge with regard to management of aEDS, particularly in adulthood. As such, systematic follow‐up and multidisciplinary treatment is essential.     

A homozygous MITF mutation leads to familial Waardenburg syndrome type 4

Waardenburg syndrome (WS) is a genetic disorder characterized by hearing loss and pigmentary abnormalities with variable penetrance. Though heterozygous mutations in MITF are a major cause for Waardenburg syndrome type 2 (WS2), homozygous mutations in this gene and the associated phenotype have been rarely characterized. In this study, we identified a novel p.R223H mutation in MITF in a Chinese Han family with variable WS features. Both parents carried a heterozygous p.R223H mutation. They had normal hearing, and premature greying of the hair is their only pigmentary abnormality. In contrast, their two children both carried a homozygous p.R223H mutation and had classic WS features including profound hearing loss, heterochromia irides and marked pigmentary abnormalities in hair and skin. Interestingly, the two affected children also have persistent chronic constipation since the neonatal period, symptoms suggestive of Waardenburg syndrome type 4 (WS4). Our study revealed a likely association between homozygous mutations in MITF and WS4, which implies a dosage effect for the underlying pathogenesis mechanism.     

Double Heterozygosity with Mutations Involving both the GJB2 and GJB6 Genes is a Possible, but very Rare, Cause of Congenital Deafness in the Czech Population

Mutations in the GJB2 gene are the most common cause of prelingual, autosomal recessive, sensorineural hearing loss worldwide. Nevertheless, 10% to 50% of patients with prelingual nonsyndromic deafness only carry one mutation in the GJB2 gene. Recently a large 342 kb deletion named Δ(GJB6‐D13S1830) involving the GJB6 gene was reported in Spanish and French deafness patients, either in a homozygous state or in combination with a monoallelic GJB2 mutation. No data have been reported about the frequency of this mutation in central Europe. Thirteen Czech patients with prelingual nonsyndromic sensorineural deafness carrying only one pathogenic mutation in the GJB2 gene were tested for the presence of the Δ(GJB6‐D13S1830) mutation. One patient with a GJB2 mutation (313del14) also carried the Δ(GJB6‐D13S1830). This is the first reported Czech case, and probably also the first central European case, of prelingual deafness due to mutations involving both the GJB2 and GJB6 genes. In addition, the Δ(GJB6‐D13S1830) was not detected in 600 control chromosomes from Czech individuals with normal hearing. We show that in the Czech Republic the Δ(GJB6‐D13S1830) is not the second most common causal factor in deafness patients heterozygous for a single GJB2 mutation, and that Δ(GJB6‐D13S1830) is very rare in central Europe compared to reports from Spain, France and Israel.     

Vestibular dysfunction in DFNB1 deafness

Mutations of GJB2 and GJB6 (connexin‐26 and 30) at the DFNB1 locus are the most common cause of autosomal recessive, nonsyndromic deafness. Despite their widespread expression throughout the vestibular system, vestibular dysfunction has not been widely recognized as a commonly associated clinical feature. The observations of vertigo accompanying DFNB1 deafness in several large families prompted our hypothesis that vestibular dysfunction may be an integral, but often overlooked, component of DFNB1 deafness. Our aim was to define the prevalence of vestibular dysfunction in Cases of DFNB1 deafness and Controls with other forms of deafness. We developed and used a survey to assess symptoms of vestibular dysfunction, medical, and family history was distributed to Cases with deafness due to pathogenic GJB2 and/or GJB6 mutations and deaf Controls without DFNB1 deafness. Our results showed: Surveys were returned by 235/515 Cases (46%) with DFNB1 mutations and 121/321 Controls (38%) without these mutations. The mean age of Cases (41) was younger than Controls (51; P < 0.001). Vestibular dysfunction was reported by 127 (54%) of Cases and was present at significantly higher rates in Cases than in deaf Controls without DFNB1 deafness (P < 0.03). Most (63%) had to lie down in order for vertigo to subside, and 48% reported that vertigo interfered with activities of daily living. Vertigo was reported by significantly more Cases with truncating than non‐truncating mutations and was also associated with a family history of dizziness. We conclude that vestibular dysfunction appears to be more common in DFNB1 deafness than previously recognized and affects activities of daily living in many patients. © 2011 Wiley‐Liss, Inc.