New syndromic form of benign hereditary chorea is associated with a deletion of TITF-1 and PAX-9 contiguous genes

Systematic review of drug therapy for chorea in NXK2-1-related disorders: Efficacy and safety evidence from case studies and series

BACKGROUND

The NKX2-1-related disorders (NKX2-1-RD) is a rare disorder characterized by choreiform movements along with respiratory and endocrine abnormalities. The European Reference Network of Rare Neurological Disorders funded by the European Commission conducted a systematic review to assess drug treatment of chorea in NKX2-1-RD, aiming to provide clinical recommendations for its management.

METHODS

A systematic pairwise review using various databases, including MEDLINE, Embase, Cochrane, CINAHL, and PsycInfo, was conducted. The review included patients diagnosed with chorea and NKX2-1-RD genetic diagnosis, drug therapy as intervention, no comparator, and outcomes of chorea improvement and adverse events. The methodological quality of the studies was assessed, and the study protocol was registered in PROSPERO.

RESULTS

Of the 1417 studies examined, 28 studies met the selection criteria, consisting of 68 patients. The studies reported 22 different treatments for chorea, including carbidopa/levodopa, tetrabenazine, clonazepam, methylphenidate, carbamazepine, topiramate, trihexyphenidyl, haloperidol, propranolol, risperidone, and valproate. No clinical improvements were observed with carbidopa/levodopa, tetrabenazine, or clonazepam, and various adverse effects were reported. However, most patients treated with methylphenidate experienced improvements in chorea and reported only a few negative effects. The quality of evidence was determined to be low.

CONCLUSIONS

The management of chorea in individuals with NKX2-1-RD presents significant heterogeneity and lack of clarity. While the available evidence suggests that methylphenidate may be effective in improving chorea symptoms, the findings should be interpreted with caution due to the limitations of the studies reviewed. Nonetheless, more rigorous and comprehensive studies are necessary to provide sufficient evidence for clinical recommendations.

Unlocking the potential of induced pluripotent stem cells for neonatal disease modeling and drug development

Neonatal lung and heart diseases, albeit rare, can result in poor quality of life, often require long-term management and/or organ transplantation. For example, Congenital Heart Disease (CHD) is one of the most common type of congenital disabilities, affecting nearly 1% of the newborns, and has complex and multifactorial causes, including genetic predisposition and environmental influences. To develop new strategies for heart and lung regeneration in CHD and neonatal lung disease, human induced pluripotent stem cells (hiPSCs) provide a unique and personalized platform for future cell replacement therapy and high-throughput drug screening. Additionally, given the differentiation potential of iPSCs, cardiac cell types such as cardiomyocytes, endothelial cells, and fibroblasts and lung cell types such Type II alveolar epithelial cells can be derived in a dish to study the fundamental pathology during disease progression. In this review, we discuss the applications of hiPSCs in understanding the molecular mechanisms and cellular phenotypes of CHD (e.g., structural heart defect, congenital valve disease, and congenital channelopathies) and congenital lung diseases, such as surfactant deficiencies and Brain-Lung-Thyroid syndrome. We also provide future directions for generating mature cell types from iPSCs, and more complex hiPSC-based systems using three-dimensional (3D) organoids and tissue-engineering. With these potential advancements, the promise that hiPSCs will deliver new CHD and neonatal lung disease treatments may soon be fulfilled.

Chromosome Microarray Analysis for the Investigation of Deletions in Pediatric Movement Disorders: A Systematic Review of the Literature

Background

Chromosome microarray analysis (CMA) can detect copy number variants (CNV) beyond the resolution of standard G-banded karyotyping. De novo or inherited microdeletions may cause autosomal dominant movement disorders.

Objectives

The purpose of this study was to analyze the clinical characteristics, associated features, and genetic information of children with deletions in known genes that cause movement disorders and to make recommendations regarding the diagnostic application of CMA.

Methods

Clinical cases published in English were identified in scientific databases (PubMed, ClinVar, and DECIPHER) from January 1998 to July 2019 following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Cases with deletions or microdeletions greater than 300 kb were selected. Information collected included age, sex, movement disorders, associated features, and the size and location of the deletion. Duplications or microduplications were not included.

Results

A total of 18.097 records were reviewed, and 171 individuals were identified. Ataxia (30.4%), stereotypies (23.9%), and dystonia (21%) were the most common movement disorders. A total of 16% of the patients demonstrated more than one movement disorder. The most common associated features were intellectual disability or developmental delay (78.9%) and facial dysmorphism (57.8%). The majority (77.7%) of microdeletions were smaller than 5 Mb. We find no correlation between movement disorders, their associated features, and the size of microdeletions.

Conclusions

Our results support the use of CMA as an investigational test in children with movement disorders. As the majority of identified articles were case reports and small case series (low quality), future efforts should focus on larger prospective studies to examine the causation of microdeletions in pediatric movement disorders.

Altered pituitary morphology as a sign of benign hereditary chorea caused by TITF1/NKX2.1 mutations

Benign hereditary chorea (BHC) is a rare genetically heterogeneous movement disorder, in which conventional neuroimaging has been reported as normal in most cases. Cystic pituitary abnormalities and features of empty sella have been described in only 7 patients with BHC to date. We present 4 patients from 2 families with a BHC phenotype, 3 of whom underwent targeted pituitary MR imaging and genetic testing. All four patients in the two families displayed a classic BHC phenotype. The targeted pituitary MR imaging demonstrated abnormal pituitary sella morphology. Genetic testing was performed in three patients, and showed mutations causing BHC in three of the patients, as well as identifying a novel nonsense mutation of the TITF1/NKX2-1 gene in one of the patients. The presence of the abnormal pituitary sella in two affected members of the same family supports the hypothesis that this sign is a distinct feature of the BHC phenotype spectrum due to mutations in the TITF1 gene. Interestingly, these abnormalities seem to develop in adult life and are progressive. They occur in at least 26% of patients affected with Brain-lung-thyroid syndrome. As a part of the management of these patients we recommend to perform follow-up MRI brain with dedicated pituitary imaging also in adult life as the abnormality can occur years after the onset of chorea.

Treatment of Chorea in Childhood

Chorea is a movement disorder characterized by ongoing random-appearing sequences of discrete involuntary movements or movement fragments. Chorea results from dysfunction of the complex neuronal networks that interconnect the basal ganglia, thalamus, and related frontal lobe cortical areas. The complexity of basal ganglia circuitry and vulnerability of those circuits to injury explains why chorea results from a wide variety of conditions. Because etiology-specific treatments or effective symptomatic treatments are available for causes of chorea, defining the underlying disease is important. The treatment of chorea can be considered in three main categories: (1) terminating or modifying exposure to the causative agent, (2) symptomatic treatment of chorea, and (3) treatment targeting the underlying etiology. Symptomatic treatment decision of chorea should be based on the functional impact on the child caused by chorea itself. There have been no reported randomized, placebo-controlled trials of symptomatic treatment for chorea in childhood. Thus the recommendations are based on clinical experience, case reports, expert opinions, and small comparative studies. Better knowledge of mechanisms underlying childhood chorea will provide more etiology-based treatments in the future.

Review of the phenotype of early-onset generalised progressive dystonia due to mutations in KMT2B

In 2016, two research groups independently identified microdeletions and pathogenic variants in the lysine-specific histone methyltransferase 2B gene, KMT2B in patients with early-onset progressive dystonia. KMT2B-dystonia (DYT28) is emerging as an important and frequent cause of childhood-onset progressive generalised dystonia and is estimated to potentially account for up to 10% of early-onset generalised dystonia. Herein, we review variants in KMT2B associated with dystonia, as well as the clinical phenotype, treatment and underlying disease mechanisms. Furthermore, in context of this newly identified condition, we summarise our approach to the genetic investigation of paediatric dystonia.

Benign hereditary chorea, not only chorea: a family case presentation

Background

Benign hereditary chorea is a rare disorder which is characterized by early onset, non-progressive choreic movement disturbance, with other hyperkinetic movements and unsteadiness also commonly seen. Hypothyroidism and lung disease are frequent additional features. The disorder is caused by mutations of the NKX2-1 gene on chromosome 14.

Case presentation

A Norwegian four-generation family with eight affected was identified. All family members had an early onset movement disorder, starting before one year of age with motor delay and chorea. Learning difficulties were commonly reported from early school years. The family presented with choreic movements at rest, but other movements were seen; myoclonus, dystonia, ataxia, stuttering and tics-like movements. All patients reported unsteadiness and ataxic gait was observed in two patients. Videos are provided in the supplementary material. Most affected family members had asthma and a subclinical or clinical hypothyroidism. Sequencing revealed a mutation in the NKX2-1 gene in all eight affected family members.

Conclusions

This is the first Norwegian family with benign hereditary chorea due to a mutation in the NKX2-1 gene, c.671 T > G (p.Leu224Arg). This family demonstrates well the wide phenotype, including dystonia, myoclonus and ataxia.

Electronic supplementary material

The online version of this article (doi:10.1186/s40673-016-0041-7) contains supplementary material, which is available to authorized users.

Benign Hereditary Chorea: An Update

Benign hereditary chorea (BHC) is a childhood-onset, hyperkinetic movement disorder normally with little progression of motor symptoms into adult life. The disorder is caused by mutations to the NKX2.1 (TITF1) gene and also forms part of the “brain–lung–thyroid syndrome”, in which additional developmental abnormalities of lung and thyroid tissue are observed. In this review, we summarize the main clinical findings in “classical” BHC syndrome and discuss more recently reported atypical features, including non-choreiform movement phenotypes. We highlight additional non-motor characteristics such as cognitive impairment and psychiatric symptoms, while discussing the evidence for BHC as a developmental disorder involving impaired neural migration and other multisystem developmental abnormalities. Finally, we will discuss the efficacy of available therapies in both affected pediatric and adult cohorts. Delineation of the BHC disease spectrum will no doubt expand our understanding of this disorder, facilitating better targeting of genetic testing and establish a framework for future clinical trials.

A novel de novo mutation of the TITF1/NKX2-1 gene causing ataxia, benign hereditary chorea, hypothyroidism and a pituitary mass in a UK family and review of the literature

Benign hereditary chorea (BHC) is a rare autosomal dominant condition characterized by early onset, non-progressive chorea, usually caused by mutations in the thyroid transcription factor-1 gene (TITF1). We describe a novel mutation arising de novo in a proband presenting in infancy with delayed walking and ataxia. She later developed chorea, then hypothyroidism and a large cystic pituitary mass. Her daughter presented in infancy with delayed walking and ataxia and went on to develop non-progressive chorea and a hormonally inactive cystic pituitary mass. Mutational analysis of the whole coding region of the TITF1 gene was undertaken and compared with a population study of 160 control subjects. This showed that both affected subjects have a heterozygous A > T substitution at nucleotide 727 of the TITF1 gene changing lysine to a stop codon at residue 211. Genetic analysis of parents and siblings of the proband confirmed that the mutation arose de novo in the proband. The mutated lysine is an evolutionarily highly conserved amino acid in the protein homoeodomain (HD) where most point mutations associated with BHC are located. The range of mutations in BHC is reviewed with particular emphasis on pituitary abnormalities. Cystic pituitary masses and abnormalities of the sella turcica are reported in just 6.4 % of published cases. This is a new nonsense mutation associated with ataxia, benign chorea and pituitary abnormalities which further extends the phenotype of this condition. Mutational screening of TITF1 is important in cases of sporadic or dominant juvenile-onset ataxia, with mild chorea where no other cause is found, particularly if pituitary abnormalities are seen on imaging.

Genetic disorders of thyroid metabolism and brain development

Normal thyroid metabolism is essential for human development, including the formation and functioning of the central and peripheral nervous system. Disorders of thyroid metabolism are increasingly recognized within the spectrum of paediatric neurological disorders. Both hypothyroid and hyperthyroid disease states (resulting from genetic and acquired aetiologies) can lead to characteristic neurological syndromes, with cognitive delay, extrapyramidal movement disorders, neuropsychiatric symptoms, and neuromuscular manifestations. In this review, the neurological manifestations of genetic disorders of thyroid metabolism are outlined, with particular focus on Allan-Herndon-Dudley syndrome and benign hereditary chorea. We report in detail the clinical features, major neurological and neuropsychiatric manifestations, molecular genetic findings, disease mechanisms, and therapeutic strategies for these emerging genetic 'brain-thyroid' disorders.

Benign hereditary chorea related to NKX2.1: expansion of the genotypic and phenotypic spectrum

AIM

Benign hereditary chorea is a dominantly inherited, childhood-onset hyperkinetic movement disorder characterized by non-progressive chorea and variable degrees of thyroid and respiratory involvement. Loss-of-function mutations in NKX2.1, a gene vital to the normal development and function of the brain, lungs, and thyroid, have been identified in a number of individuals.

METHOD

Clinical data from individuals with benign hereditary chorea identified through paediatric neurology services were collected in a standardized format. The NKX2.1 gene was analysed by Sanger sequencing, multiplex ligation-dependent probe amplification, and microarray analysis.

RESULTS

Six of our cohort were female and four male, median age at assessment was 8 years 6 months (range 1 y 6 mo-18 y). We identified 10 probands with NKX2.1 mutations; nine of these mutations are novel (including two whole-gene deletions) and one has been previously reported. Of the 10 individuals, eight presented with muscle hypotonia and four had evidence of hypothyroidism or respiratory involvement. Only three out of the 10 individuals had the full triad of 'brain-lung-thyroid syndrome' symptoms. Additional clinical characteristics occurring in individual participants included growth hormone deficiency, pes cavus, kyphosis, duplex kidney, and obsessive-compulsive disorder.

INTERPRETATION

Our data suggest that the neurological phenotype is prominent in this condition and that many patients with benign hereditary chorea do not have the classic triad of brain-lung-thyroid syndrome. The extended phenotype may include obsessive-compulsive disorder and skeletal abnormalities.

Comprehensive genotyping and clinical characterisation reveal 27 novel NKX2-1 mutations and expand the phenotypic spectrum

BACKGROUND

NKX2-1 encodes a transcription factor with large impact on the development of brain, lung and thyroid. Germline mutations of NKX2-1 can lead to dysfunction and malformations of these organs. Starting from the largest coherent collection of patients with a suspected phenotype to date, we systematically evaluated frequency, quality and spectrum of phenotypic consequences of NKX2-1 mutations.

METHODS

After identifying mutations by Sanger sequencing and array CGH, we comprehensively reanalysed the phenotype of affected patients and their relatives. We employed electrophoretic mobility shift assay (EMSA) to detect alterations of NKX2-1 DNA binding. Gene expression was monitored by means of in situ hybridisation and compared with the expression level of MBIP, a candidate gene presumably involved in the disorders and closely located in close genomic proximity to NKX2-1.

RESULTS

Within 101 index patients, we detected 17 point mutations and 10 deletions. Neurological symptoms were the most consistent finding (100%), followed by lung affection (78%) and thyroidal dysfunction (75%). Novel symptoms associated with NKX2-1 mutations comprise abnormal height, bouts of fever and cardiac septum defects. In contrast to previous reports, our data suggest that missense mutations in the homeodomain of NKX2-1 not necessarily modify its DNA binding capacity and that this specific type of mutations may be associated with mild pulmonary phenotypes such as asthma. Two deletions did not include NKX2-1, but MBIP, whose expression spatially and temporarily coincides with NKX2-1 in early murine development.

CONCLUSIONS

The high incidence of NKX2-1 mutations strongly recommends the routine screen for mutations in patients with corresponding symptoms. However, this analysis should not be confined to the exonic sequence alone, but should take advantage of affordable NGS technology to expand the target to adjacent regulatory sequences and the NKX2-1 interactome in order to maximise the yield of this diagnostic effort.

The molecular causes of thyroid dysgenesis: a systematic review

BACKGROUND

Congenital hypothyroidism (CH) is a frequent disease occurring with an incidence of about 1/2500 newborns/year. In 80-85% of the cases CH is caused by alterations in thyroid morphogenesis, generally indicated by the term "thyroid dysgenesis" (TD). TD is generally a sporadic disease, but in about 5% of the cases a genetic origin has been demonstrated. In these cases, mutations in genes playing a role during thyroid morphogenesis (NKX2-1, PAX8, FOXE1, NKX2-5, TSHR) have been reported.

AIM

This work reviews the main steps of thyroid morphogenesis and all the genetic alterations associated with TD and published in the literature.

Identification and functional characterization of a novel mutation in the NKX2-1 gene: comparison with the data in the literature

BACKGROUND

NKX2-1 mutations have been described in several patients with primary congenital hypothyroidism, respiratory distress, and benign hereditary chorea, which are classical manifestations of the brain-thyroid-lung syndrome (BTLS).

METHODS

The NKX2-1 gene was sequenced in the members of a Brazilian family with clinical features of BTLS, and a novel monoallelic mutation was identified in the affected patients. We introduced the mutation in an expression vector for the functional characterization by transfection experiments using both thyroidal and lung-specific promoters.

RESULTS

The mutation is a deletion of a cytosine at position 834 (ref. sequence NM_003317) (c.493delC) that causes a frameshift with formation of an abnormal protein from amino acid 165 and a premature stop at position 196. The last amino acid of the nuclear localization signal, the whole homeodomain, and the carboxy-terminus of NKX2-1 are all missing in the mutant protein, which has a premature stop codon at position 196 (p.Arg165Glyfs*32). The p.Arg165Glyfs*32 mutant does not bind DNA, and it is unable to transactivate the thyroglobulin (Tg) and the surfactant protein-C (SP-C) promoters. Interestingly, a dose-dependent dominant negative effect of the p.Arg165Glyfs*32 was demonstrated only on the Tg promoter, but not on the SP-C promoter. This effect was also noticed when the mutation was tested in presence of PAX8 or cofactors that synergize with NKX2-1 (P300 and TAZ). The functional effect was also compared with the data present in the literature and demonstrated that, so far, it is very difficult to establish a specific correlation among NKX2-1 mutations, their functional consequence, and the clinical phenotype of affected patients, thus suggesting that the detailed mechanisms of transcriptional regulation still remain unclear.

CONCLUSIONS

We describe a novel NKX2-1 mutation and demonstrate that haploinsufficiency may not be the only explanation for BTLS. Our results indicate that NKX2-1 activity is also finely regulated in a tissue-specific manner, and additional studies are required to better understand the complexities of genotype-phenotype correlations in the NKX2-1 deficiency syndrome.

Choreoathetosis, congenital hypothyroidism and neonatal respiratory distress syndrome with intact NKX2-1

Mutations in the NK2 homeobox 1 gene (NKX2-1) cause a rare syndrome known as choreoathetosis, congenital hypothyroidism, and neonatal respiratory distress syndrome (OMIM 610978). Here we present the first reported patient with this condition caused by a 14q13.3 deletion which is adjacent to but does not interrupt NKX2-1, and review the literature on this condition. The infant presented at 23 months with a history of developmental delay, hyperkinesia, recurrent respiratory infections, neonatal respiratory distress, and hypothyroidism. Choreiform movements and delayed motor milestones were first noted at 6-8 months of age. TSH levels had been consistently elevated from 8 months of age. The clinical presentation was suggestive of an NKX2-1 mutation. Sequencing of all exons and splice site junctions of NKX2-1 was performed but was normal. Array CGH was then performed and a 3.29 Mb interstitial deletion at 14q13.1-q13.3 was detected. The distal region of loss of the deletion disrupted the surfactant associated 3 (SFTA3) gene but did disrupt NKX2-1. Findings were confirmed on high resolution SNP array and multiplex semiquanitative PCR. NKX2-1 encodes transcriptional factors involved in the developmental pathways for thyroid, lung, and brain. We hypothesize that the region centromeric to NKX2-1 is important for the normal functioning of this gene and when interrupted produces a phenotype that is typical of the choreoathetosis, congenital hypothyroidism, and neonatal respiratory distress syndrome, as seen in our patient. We conclude that deletions at 14q13.3 adjacent to but not involving NKX2-1 can cause choreoathetosis, congenital hypothyroidism, and neonatal respiratory distress syndrome.

Benign hereditary chorea: dopaminergic brain imaging in patients with a novel intronic NKX2.1 gene mutation

Mutations in the NKX2.1 gene, which is essential for the development, differentiation and organization of the basal ganglia, cause benign hereditary chorea (BHC) characterized by childhood-onset non-progressive chorea. We herein report the clinical features of six patients from a single family with a novel intronic mutation and present the dopaminergic neuronal imaging by using positron emission tomography (PET) imaging to assess the integrity of the striatal dopaminergic system using [(11)C]-CFT for the presynaptic dopamine transporter function and [(11)C]-raclopride for the postsynaptic D2 receptor function. The patients showed mild generalized chorea without either congenital hypothyroidism or a history of pulmonary infection and some of the patients had goiter. Genetic analyses of NKX2.1 gene showed a novel heterozygous c.464-9C>A mutation that created a new acceptor splice site resulting in the production of an aberrant transcript with a 7-bp insertion identical to a intronic sequence of genomic DNA. Oral levodopa failed to improve the involuntary movement, while haloperidol, a dopamine D2 receptor blocking agent, exacerbated the choric movement in a single patient. The dopaminergic PET studies in the two patients revealed decreased raclopride binding in the striatum, while the CFT binding was not altered. The impairment of D2 receptor function in the basal ganglia may result in exacerbation of the chorea induced by haloperidol. The molecular brain imaging and therapeutic response may help elucidate the pathophysiological mechanism of the motor control in the BHC-associated NKX2.1 mutation.

Microdeletions detected using chromosome microarray in children with suspected genetic movement disorders: a single-centre study

AIM

Chromosome microarray (CMA) can determine copy number variants such as microdeletions or microduplications. Microdeletions of movement disorder genes including epsilon-sarcoglycan (SGCE) and thyroid transcription factor-1 (TITF1) have been described in patients with myoclonus dystonia and benign hereditary chorea respectively. We examined whether CMA is a valuable tool in the investigation of children with suspected genetic movement disorders.

METHOD

A genetic movement disorder was suspected if there was a positive first-degree family history, or two or more of the following factors: normal or near-normal magnetic resonance imaging, negative history of brain injury, and negative investigations for metabolic disorders. Tic disorders were excluded. Twenty-five patients (18 males, seven females) with a mean age at movement disorder onset of 4 years 5 month (range 1 mo-14 y) were prospectively recruited with the following primary movement disorders: dystonia (n=10), paroxysmal kinesigenic dyskinesia (n=5), tremor (n=4), chorea (n=3), myoclonus (n=2), and paroxysmal non-kinesigenic dyskinesia (n=1). Comorbid associated features were common, particularly developmental delay or intellectual disability (19 out of 25) and attention-deficit-hyperactivity disorder (six out of 25). CMA was performed using Agilent aCGH 60K array.

RESULTS

Seven out of twenty-five patients had a microdeletion determined by CMA. None of the microdeletions were considered benign variants. Four patients had a deletion of a known movement disorder gene including paroxysmal kinesigenic dyskinesia (PRRT2; n=2), SGCE (myoclonus dystonia, n=1), and TITF1 (benign hereditary chorea, n=1). Three patients had novel microdeletions of unknown but potential significance including 14q13.3 (chorea, n=1), 19p13.12 (tremor, n=1), and 19q13.12 (progressive dystonia). All seven patients had associated neurodevelopmental or behavioural problems.

INTERPRETATION

Assays that determine copy number variants may be a valuable first-tier investigation in patients with suspected genetic movement disorders, particularly when associated with intellectual disability or developmental disorders. Microdeletion syndromes may help the search for new movement disorder genes.

A national internet-linked based database for pediatric interstitial lung diseases: the French network

BACKGROUND

Interstitial lung diseases (ILDs) in children represent a heterogeneous group of rare respiratory disorders that affect the lung parenchyma. After the launch of the French Reference Centre for Rare Lung Diseases (RespiRare®), we created a national network and a web-linked database to collect data on pediatric ILD.

METHODS

Since 2008, the database has been set up in all RespiRare® centres. After patient's parents' oral consent is obtained, physicians enter the data of children with ILD: identity, social data and environmental data; specific aetiological diagnosis of the ILD if known, genetics, patient visits to the centre, and all medical examinations and tests done for the diagnosis and/or during follow up. Each participating centre has a free access to his own patients' data only, and cross-centre studies require mutual agreement. Physicians may use the system as a daily aid for patient care through a web-linked medical file, backed on this database.

RESULTS

Data was collected for 205 cases of ILD. The M/F sex ratio was 0.9. Median age at diagnosis was 1.5 years old [0-16.9]. A specific aetiology was identified in 149 (72.7%) patients while 56 (27.3%) cases remain undiagnosed. Surfactant deficiencies and alveolar proteinosis, haemosiderosis, and sarcoidosis represent almost half of the diagnoses. Median length of follow-up is 2.9 years [0-17.2].

CONCLUSIONS

We introduce here the French network and the largest national database in pediatric ILDs. The diagnosis spectrum and the estimated incidence are consistent with other European databases. An important challenge will be to reduce the proportion of unclassified ILDs by a standardized diagnosis work-up. This database is a great opportunity to improve patient care and disease pathogenesis knowledge. A European network including physicians and European foundations is now emerging with the initial aim of devising a simplified European database/register as a first step to larger European studies.

Update on the Non-Huntington's Disease Choreas with Comments on the Current Nomenclature

CHOREA CAN BE CAUSED BY A MULTITUDE OF ETIOLOGIES: neurodegenerative, pharmacological, structural, metabolic, and others. In absence of other apparent causes, exclusion of Huntington's disease is often a first step in the diagnostic process. There are a number of neurodegenerative disorders whose genetic etiology has been identified in the past decade. Molecular diagnosis has enabled genetic identification of disorder subtypes which were previously grouped together, such as the neurodegeneration with brain iron accumulation disorders and the neuroacanthocytosis syndromes, as well as identification of phenotypic outliers for recognized disorders. Correct molecular diagnosis is essential for genetic counseling and, hopefully, ultimately genetic therapies. In addition, there has recently been recognition of other disorders which can mimic neurodegenerative disorders, including paraneoplastic and prion disorders. This article focuses upon recent developments in the field but is not intended to provide an exhaustive review of all causes of chorea, which is available elsewhere. I also discuss the nomenclature of these disorders which has become somewhat unwieldy, but may ultimately be refined by association with the causative gene.

[Genetic disorders of surfactant]

Lung diseases associated with surfactant metabolism disorders represent a significant but heterogeneous group of rare disorders. Intra-alveolar accumulation of protein related to surfactant dysfunction leads to cough, hypoxemia and radiological diffuse infiltration. Inherited deficiency of pulmonary surfactant protein B (SP-B) was initially described in term newborns who develop severe respiratory failure at birth. More recently, mutations in surfactant protein C (SP-C) or in proteins required for surfactant synthesis such as ATP-binding cassette, sub-family A, member 3 (ABCA3) or NK2 homeobox 1 (NKX2-1) were identified in newborns with respiratory distress but also in children with diffuse infiltrative pneumonia. The aim of this review is to describe the clinical presentation of these diseases but also the diagnostic tools and the treatments options available.

Brain-lung-thyroid disease: clinical features of a kindred with a novel thyroid transcription factor 1 mutation

Brain-lung-thyroid disease is a rare familial disorder caused by mutations in thyroid transcription factor 1, a gene that regulates neuronal migration. We report the clinical features of ten patients from a single family with a novel gene mutation, including observations regarding treatment. Neurologic features of the kindred included developmental delay, learning difficulties, psychosis, chorea, and dystonia. Three patients had a history of seizure, which has not been previously reported in genetically confirmed cases. Low-dose dopamine-receptor blocking drugs were poorly tolerated in 2 patients who received this therapy, levodopa improved chorea in 3 of 4 children, and diazepam was markedly effective in a single adult patient. Chorea related to brain-lung-thyroid disease appears to respond paradoxically to antidopaminergic drugs. The unusual therapeutic response seen in our patients and others may help elucidate how disease-related migratory deficits affect neural pathways associated with motor control.

A novel nonsense mutation in the TITF-1 gene in a Japanese family with benign hereditary chorea

A Japanese family with a novel nonsense mutation in the TITF-1 gene (p.Y98X) is described. The proband showed severe generalized chorea, delayed motor development, subnormal intelligence, congenital hypothyroidism, bronchial asthma, and a history of pulmonary infection, all of which are characteristic features of Brain-Thyroid-Lung syndrome. On the other hand, her brother and mother showed a mild benign hereditary chorea (BHC) phenotype with congenital hypothyroidism. Intrafamilial phenotypic variation is common in BHC/Brain-Thyroid-Lung syndrome and suggests the existence of other genetic or environmental factors regulating TITF-1 function. Although choreic movement in BHC/Brain-Thyroid-Lung syndrome is recognized as non-progressive, the proband showed re-exacerbation of choreic movement at puberty. The dopamine agonist, ropinirole hydrochloride, reduced her choreic movements, suggesting that levodopa and/or dopamine agonists may compensate for underdeveloped dopaminergic pathways in this disorder.

Benign hereditary chorea: an update

Benign hereditary chorea (BHC, MIM 118700) is a rare autosomal dominant disorder manifesting with chorea in conjunction with hypothyroidism and respiratory problems, a triad also named "brain-lung-thyroid syndrome". BHC is characterized by childhood onset with minimal or no progression into adult life and normal cognitive function. The genetic basis of BHC has been partially resolved, when mutations in the TTF1 gene on chromosome 14q13 encoding the thyroid transcription factor-1 have been identified in a number of BHC patients, suggesting that aberration of TTF1 transcriptional function or haploinsufficiency is associated with this disorder. TTF1 (also known as TITF1, TEBP or NKX2-1), belonging to the NKX2 homeodomain transcription factor family, has been implicated in several important molecular pathways essential for brain, thyroid and lung morphogenesis. Clinical evaluation of TTF1 gene mutations carrier patients exposed the involvement of each of the triad's components characterized by heterogeneity between index cases and even within families. This review highlights the current updates on expanded clinical aspects of BHC, imaging and treatment experience, its genetic markers, proposed molecular mechanisms, animal models and link to cancer.

Benign hereditary chorea

Benign hereditary chorea (BHC) is a hyperkinetic movement disorder that historically has been characterized as a nonprogressive, dominantly inherited, childhood-onset chorea with normal intelligence. However, in some cases, atypical features were described such that controversy arose regarding whether BHC was a single syndrome. In 2002, a candidate gene, thyroid transcription factor (TITF-1), was identified to cause at least some cases of BHC. Since that time, the classical phenotype has expanded further to include "brain-thyroid-lung syndrome," which, in addition to the neurological symptoms, also manifests variable degrees of thyroid and lung abnormalities. Pathophysiologic mechanisms by which symptoms can occur are postulated to include haploinsufficiency (loss of function) and/or dominant negative effect on wild-type protein. However, genotype-phenotype correlations are complex and there is no clear relationship between mutation size, location or type of mutation, and severity of phenotype. Gross and microscopic pathology has been unremarkable, though immunohistochemistry suggests that BHC may manifest as a result of a reduced complement of migratory interneurons to the striatum and cortex. This chapter reviews the historical literature and current understanding regarding this familial, developmental disorder.

A 223-kb de novo deletion of PAX9 in a patient with oligodontia

The PAX (paired box) genes are a family of transcription factors critical for fetal growth and organogenesis. Abnormalities of PAX2, PAX3, PAX6, and PAX9 are associated with various congenital craniofacial anomalies, including tooth abnormalities. We present here a boy with oligodontia and language delay. Dental x-rays showed that he lacked primary molars and was missing most of his permanent teeth. A genome-wide, single-nucleotide polymorphism-based microarray revealed a de novo 223-kb heterozygous deletion on 14q13.3 that included the PAX9 gene. In addition, the array showed 2 copies of the X chromosome and 1 copy of the Y chromosome, diagnostic for Klinefelter syndrome. The findings in this patient illustrate the role of the PAX9 gene in tooth development and provide the first example of a de novo deletion of 14q13.3 manifesting primarily with oligodontia. This report also supports the utility of genome-wide microarrays in determining the genetic cause of craniofacial abnormalities.

A novel g.-1258G>A mutation in a conserved putative regulatory element of PAX9 is associated with autosomal dominant molar hypodontia

Mutations in the transcription factor PAX9 which plays a critical role in the switching of odontogenic potential from the epithelium to the mesenchyme during tooth development cause autosomal dominant non-syndromic hypodontia primarily affecting molars. Linkage analysis on a family segregating autosomal dominant molar hypodontia with markers flanking and within PAX9 yielded a maximum multipoint LOD score of 3.6. No sequence variants were detected in the coding or 5'- and 3'-untranslated regions (UTRs) of PAX9. However, we identified a novel g.-1258G>A sequence variant in all affected individuals of the family but not in the unaffected family members or in 3088 control chromosomes. This mutation is within a putative 5'-regulatory sequence upstream of PAX9 highly conserved in primates, somewhat conserved in ungulates and carnivores but not conserved in rodents. Bioinformatics analysis of the sequence determined that there was no abolition or creation of a putative binding site for known transcription factors. Based on our previous findings that haploinsufficiency for PAX9 leads to hypodontia, we postulate that the g.-1258G>A variant reduces the expression of PAX9 which underlies the hypodontia phenotype in this family.

Interstitial lung diseases in children

Interstitial lung disease (ILD) in infants and children comprises a large spectrum of rare respiratory disorders that are mostly chronic and associated with high morbidity and mortality. These disorders are characterized by inflammatory and fibrotic changes that affect alveolar walls. Typical features of ILD include dyspnea, diffuse infiltrates on chest radiographs, and abnormal pulmonary function tests with restrictive ventilatory defect and/or impaired gas exchange. Many pathological situations can impair gas exchange and, therefore, may contribute to progressive lung damage and ILD. Consequently, diagnosis approach needs to be structured with a clinical evaluation requiring a careful history paying attention to exposures and systemic diseases. Several classifications for ILD have been proposed but none is entirely satisfactory especially in children. The present article reviews current concepts of pathophysiological mechanisms, etiology and diagnostic approaches, as well as therapeutic strategies. The following diagnostic grouping is used to discuss the various causes of pediatric ILD: 1) exposure-related ILD; 2) systemic disease-associated ILD; 3) alveolar structure disorder-associated ILD; and 4) ILD specific to infancy. Therapeutic options include mainly anti-inflammatory, immunosuppressive, and/or anti-fibrotic drugs. The outcome is highly variable with a mortality rate around 15%. An overall favorable response to corticosteroid therapy is observed in around 50% of cases, often associated with sequelae such as limited exercise tolerance or the need for long-term oxygen therapy.

Genetic Basis of Children's Interstitial Lung Disease

Specific genetic causes for children's interstitial lung disease (chILD) have been identified within the past decade. These include deletions of or mutations in genes encoding proteins important in surfactant production and function (SP-B, SP-C, and ABCA3), surfactant catabolism (GM-CSF receptor), as well as transcription factors important for surfactant production (TTF1) or lung development (Fox F1), with heterozygous deletions or loss-of-function mutations of the latter resulting in alveolar capillary dysplasia (ACD) with misalignment of the pulmonary veins. Familial pulmonary fibrosis in adults may result from mutations in genes encoding components of telomerase and SP-A2. While not yet reported in children, the expression of these genes in alveolar type II epithelial cells supports a key role for the disruption of normal homeostasis in this cell type in the pathogenesis of interstitial lung disease. The identification of specific genetic causes for chILD now allows for the possibility of non-invasive diagnosis, and provides insight into basic cellular mechanisms that may allow the development of novel therapies.

Ongoing expression of Nkx2.1 in the postnatal mouse forebrain: potential for understanding NKX2.1 haploinsufficiency in humans?

Coordinated movements require the caudate-putamen and the globus pallidus, two nuclei belonging to the basal ganglia, to be intact and functioning properly. Many neurons populating these regions derive from the medial ganglionic eminence, a transient structure that expresses the transcription factor Nkx2.1 during prenatal development. Accordingly, the basal ganglia of Nkx2.1(-/-) mice are heavily affected and a substantial loss of several types of GABAergic interneurons has been observed. Interestingly, heterozygous mutation of the NKX2.1 gene in humans has been described as causing an unusual disorder from the second year of life onwards, which is mainly characterized by disturbances of motor abilities and delayed speech development. In the present study, we therefore investigated whether Nkx2.1 is still expressed in the young adult and aged mouse forebrain. After birth, the most intense immunolabeling for Nkx2.1 was detected in several components of the hypothalamic region, in the subventricular zone of the ventral tips lining the lateral ventricles, and in neighboring structures including the striatum, the globus pallidus and the various nuclei of the septal complex. Surprisingly, this staining pattern was substantially maintained into adulthood. Double immunocytochemistry for Nkx2.1 and various neuronal markers revealed that mainly parvalbumin-containing GABAergic neurons, but also cholinergic neurons, of the ventral forebrain express this protein. Moreover, in situ hybridization confirmed that these neurons maintain synthesis of Nkx2.1 throughout life. The robust expression of Nkx2.1 by these neurons points to a broad functional spectrum within the adult forebrain.

Genetic basis of tooth agenesis

Tooth agenesis or hypodontia, failure to develop all normally developing teeth, is one of the most common developmental anomalies in man. Common forms, including third molar agenesis and hypodontia of one or more of the incisors and premolars, constitute the great majority of cases. They typically affect those teeth that develop latest in each tooth class and these teeth are also most commonly affected in more severe and rare types of tooth agenesis. Specific vulnerability of the last developing teeth suggests that agenesis reflects quantitative defects during dental development. So far molecular genetics has revealed the genetic background of only rare forms of tooth agenesis. Mutations in MSX1, PAX9, AXIN2 and EDA have been identified in familial severe agenesis (oligodontia) and mutations in many other genes have been identified in syndromes in which tooth agenesis is a regular feature. Heterozygous loss of function mutations in many genes reduce the gene dose, whereas e.g. in hypohidrotic ectodermal dysplasia (EDA) the complete inactivation of the partially redundant signaling pathway reduces the signaling centers. Although these mechanisms involve quantitative disturbances, the phenotypes associated with mutations in different genes indicate that in addition to an overall reduction of odontogenic potential, tooth class-specific and more complex mechanisms are also involved. Although several of the genes so far identified in rare forms of tooth agenesis are being studied as candidate genes of common third molar agenesis and incisor and premolar hypodontia, it is plausible that novel genes that contribute to these phenotypes will also become identified.

Psychosis, short stature in benign hereditary chorea: a novel thyroid transcription factor-1 mutation

Benign hereditary chorea (BHC) is a rare autosomal dominant nonprogressive movement disorder. In some cases the phenotype includes, besides choreoathetosis, thyroid dysfunction and pulmonary infections in infancy, as expressed by the name "Brain-Thyroid-Lung syndrome". Mutations in the thyroid transcription factor-1 (TITF-1) gene have been identified in some BHC families. We present the phenotypic features of a family with chorea, hypothyroidism, and lung dysfunction. All affected individuals suffered from a nonprogressive chorea with infancy onset. All showed short stature and some webbed neck. One patient suffered from psychosis at the age of 27 years another from lung carcinoma. In all affected individuals, a novel mutation consisting of heterozygous C to A substitution at position 650 of the coding sequence of the TITF-1 gene, exon 3 was detected, leading to a premature stop at codon 217 (S217X). We describe the unique phenotypic features and intrafamilial variability expressing this novel mutation.

Five new TTF1/NKX2.1 mutations in brain-lung-thyroid syndrome: rescue by PAX8 synergism in one case

Thyroid transcription factor 1 (NKX2-1/TITF1) mutations cause brain-lung-thyroid syndrome, characterized by congenital hypothyroidism (CH), infant respiratory distress syndrome (IRDS) and benign hereditary chorea (BHC). The objectives of the present study were (i) detection of NKX2-1 mutations in patients with CH associated with pneumopathy and/or BHC, (ii) functional analysis of new mutations in vitro and (iii) description of the phenotypic spectrum of brain-lung-thyroid syndrome. We identified three new heterozygous missense mutations (L176V, P202L, Q210P), a splice site mutation (376-2A-->G), and one deletion of NKX2-1 at 14q13. Functional analysis of the three missense mutations revealed loss of transactivation capacity on the human thyroglobulin enhancer/promoter. Interestingly, we showed that deficient transcriptional activity of NKX2-1-P202L was completely rescued by cotransfected PAX8-WT, whereas the synergistic effect was abolished by L176V and Q210P. The clinical spectrum of 6 own and 40 published patients with NKX2-1 mutations ranged from the complete triad of brain-lung-thyroid syndrome (50%), brain and thyroid disease (30%), to isolated BHC (13%). Thyroid morphology was normal (55%) and compensated hypothyroidism occurred in 61%. Lung disease occurred in 54% of patients (IRDS at term 76%; recurrent pulmonary infections 24%). On follow-up, 20% developed severe chronic interstitial lung disease, and 16% died. In conclusion, we describe five new NKX2.1 mutations with, for the first time, complete rescue by PAX8 of the deficient transactivating capacity in one case. Additionally, our review shows that the majority of affected patients display neurological and/or thyroidal problems and that, although less frequent, lung disease is responsible for a considerable mortality.

Deletion of PAX9 and oligodontia: a third family and review of the literature

OBJECTIVE

This study was conducted to report a family affected by benign hereditary chorea in which a large deletion including TTF1, PAX9, and other genes was identified and results in oligodontia.

METHODS

Clinical and radiological studies of the two affected members (mother and daughter) were used to describe the oligodontia present in both of them.

RESULTS

The missing teeth in both patients are described in detail, and these data are compared with the dental anomalies observed in the only two other families with deletions of PAX9 and with the data available for 12 previously reported families carrying different types of PAX9 mutations.

CONCLUSIONS

There is a clinical relevance for recognizing such families, and offering available therapies since childhood is stressed. Some genotype-phenotype correlations between PAX9 mutations and dental anomalies can be drawn.

A novel NKX2.1 mutation in a family with hypothyroidism and benign hereditary chorea

BACKGROUND

We studied a boy with congenital hypothyroidism, benign hereditary chorea, and respiratory distress. His mother and his grandfather were affected by hypothyroidism with a late onset and benign hereditary chorea. The aim of this study was to establish the genetic defects that cause that phenotype and study the molecular mechanisms of the pathology.

METHODS

NKX2.1, PAX8, NKX2.5, and TAZ genes were sequenced.

RESULTS

Direct sequencing of the NKX2.1 gene showed, in all the affected, a new heterozygous mutation from cytosine to adenine in the second base of the triplet encoding for the amino acid at position 145. The mutation (C609A) is responsible for a change from serine to a stop codon (S145X). We also demonstrated that the mutant protein is predominantly in the cytoplasm and unable to translocate into the nucleus. Of note, the S145X mutation produces variable phenotypes in the affected members of the family. No mutations have been identified in the NKX2.5, PAX8, and TAZ genes.

CONCLUSIONS

Our study extends the knowledge of the functional effect of NKX2.1 mutations and further highlights the complexities of genotype-phenotype correlation in the NKX2.1 deficiency syndromes.

Benign hereditary chorea revisited: a journey to understanding

Benign hereditary chorea (BHC) has been characterized as an autosomal dominant disorder manifesting nonprogressive chorea without dementia. However, there has been controversy regarding its existence. Diagnosis has been based solely on clinical criteria with many patients and families demonstrating "atypical" features and until recently, no diagnostic test was available for confirmation. Since 2002, mutations in the thyroid transcription factor (TITF-1) gene have been identified as resulting in some cases of BHC. Additionally, the clinical spectrum has expanded to include abnormalities in thyroid and lung with the putative mechanism of disease resulting from gene haploinsufficiency and reduced protein product. This review summarizes both a historical perspective and our current understanding of BHC.

Clinical differentiation of genetically proven benign hereditary chorea and myoclonus-dystonia

Because of clinical similarities, benign hereditary chorea and myoclonus-dystonia (DYT11) might be confused. No systematic comparisons of genetically proven cases with thyroid transcription factor-1 (TITF-1) and epsilon-sarcoglycan (SGCE) mutations have been performed to date. Three index patients and one index patients' daughter underwent genetic analysis of the TITF-1 and the SGCE gene. The movement disorders of all patients were assessed by video review. A new splicing mutation (376-2A>C) of the TITF-1 gene was detected in a mother and her daughter. Two additional patients carried a de novo SGCE nonsense mutation in exon 3 (R97X) and a novel SGCE missense mutation in exon 6 (G227V). Both TITF-1 mutation carriers presented with infancy-onset, nonprogressive chorea, which responded to alcohol intake. In addition, dystonia of the neck and trunk as well as fleeting jerky movements of the distal limbs could be observed. The mutually exclusive appearance of lightning-like myoclonic jerks triggered by action in SGCE mutation carriers and of continuous chorea of all limbs in TITF-1 mutation carriers phenotypically discriminated both genetic disorders. TITF-1 mutations should be considered in choreiform movement disorders with onset in infancy even in the presence of dystonia and myoclonic jerks.

Functional characterization of a novel mutation in TITF-1 in a patient with benign hereditary chorea

Benign hereditary chorea (BHC) is an autosomal dominant disorder of early onset characterised by non progressive choreic movements with normal cognitive function occasionally associated with hypothyroidism and respiratory problems. Numerous pieces of evidence link BHC with TITF-1/NKX2.1 gene mutations. We studied a patient with a familial benign hereditary chorea and normal thyroid and respiratory function. Sequence analysis of TITF-1 revealed the presence of a heterozygous C>T substitution at nucleotide 532, predicted to change an arginine (CGA) with a stop codon (TGA) at position 178 (R178X). A functional analysis shows that the mutated TTF-1 is not binding DNA, nor activating the canonical thyroid target gene promoter or interfering with the ability of wild type TTF-1 to activate transcription. In addition, the mutated protein is predominantly cytoplasmic, rather than nuclear as in the case of the wild type TTF-1. Thus, we have identified a new mutation in the TTF-1 coding gene in a patient with benign hereditary chorea. The results show that the mutation leads to a haploinsufficiency of TITF-1 and opens the question of genotype/phenotype correlation.