Mutations in two large pedigrees highlight the role of ZNF711 in X-linked intellectual disability.

Intellectual disability (ID) affects approximately 1-2% of the general population and is characterized by impaired cognitive abilities. ID is both clinically as well as genetically heterogeneous, up to 2000 genes are estimated to be involved in the emergence of the disease with various clinical presentations. For many genes, only a few patients have been reported and causality of some genes has been questioned upon the discovery of apparent loss-of-function mutations in healthy controls. Description of additional patients strengthens the evidence for the involvement of a gene in the disease and can clarify the clinical phenotype associated with mutations in a particular gene. Here, we present two large four-generation families with a total of 11 males affected with ID caused by mutations in ZNF711, thereby expanding the total number of families with ID and a ZNF711 mutation to four. Patients with mutations in ZNF711 all present with mild to moderate ID and poor speech accompanied by additional features in some patients, including autistic features and mild facial dysmorphisms, suggesting that ZNF711 mutations cause non-syndromic ID.

Eficacia de los programas de ejercicios de motricidad oral para el tratamiento logopédico de las dificultades de habla / Non-speech oral motor treatment efficacy for children with developmental speech sound disorders

Introducción. En el tratamiento logopédico de las dificultades de habla se practican dos enfoques metodológicos antagó-nicos: los no verbales, basados en ejercicios de motricidad oral (EMO), y los verbales, que se basan en tareas de procesamiento de habla con sílabas, fonemas y palabras. En España, los programas de EMO se llaman ‘programas de praxias’, están muy difundidos y son apreciados por los logopedas. Objetivo. Revisar los estudios sobre la eficacia de los tratamientos basados en EMO aplicados a niños con trastornos de habla y los argumentos teóricos que podrían justificar o no su utilidad. Desarrollo. Durante las últimas décadas se han acumulado pruebas sobre la falta de eficacia de este enfoque en el tratamiento de los trastornos evolutivos del habla y en las dificultades de pronunciación de poblaciones sin alteración neurológica de la función motriz. La American Speech-Language-Hearing Association ha desaconsejado su uso atendiendo a los principios de práctica basada en la evidencia. Los conocimientos acumulados sobre el control motor demuestran que el patrón de movilidad y su correspondiente organización cerebral son diferentes en el habla y en otras funciones no verbales ligadas a la alimentación y la respiración. Conclusiones. Ni los estudios sobre su eficacia ni los argumentos a partir de estudios del control motor aconsejan el uso de los programas basados en EMO para el tratamiento de las dificultades de pronunciación en niños con trastornos evolutivos del lenguaje (AU)

Introduction. In the treatment of speech disorders by means of speech therapy two antagonistic methodological approaches are applied: non-verbal ones, based on oral motor exercises (OME), and verbal ones, which are based on speech processing tasks with syllables, phonemes and words. In Spain, OME programmes are called ‘programas de praxias’, and are widely used and valued by speech therapists. Aim. To review the studies conducted on the effectiveness of OME-based treatments applied to children with speech disorders and the theoretical arguments that could justify, or not, their usefulness. Development. Over the last few decades evidence has been gathered about the lack of efficacy of this approach to treat developmental speech disorders and pronunciation problems in populations without any neurological alteration of motor functioning. The American Speech-Language-Hearing Association has advised against its use taking into account the principles of evidence-based practice. The knowledge gathered to date on motor control shows that the pattern of mobility and its corresponding organisation in the brain are different in speech and other non-verbal functions linked to nutrition and breathing. Conclusions. Neither the studies on their effectiveness nor the arguments based on motor control studies recommend the use of OME-based programmes for the treatment of pronunciation problems in children with developmental language disorders (AU)

End-word dysfluencies in young children: a clinical report.

OBJECTIVE: We report on 12 children with end-word dysfluencies (EWDs). Our aim was to document this little-reported type of dysfluency and to develop a possible explanation for them and how they relate to developmental stuttering. METHOD: Audio recordings were made for 9 of the 12 children in the study. The EWDs were identified by consensus of two specialist speech pathologists and confirmed on acoustic displays. A segment of participant 1's speech was transcribed, including phonetic transcription of EWDs. RESULTS: The EWDs typically consisted of repetitions of the nucleus and/or the coda. However, there were also some EWDs that consisted of fixed postures on the nucleus (when in final position) or coda. We also report on the infrequent occurrence of broken words. Ten of the 12 children also stuttered, with 9 of them coming from four families, each with a history of stuttering. CONCLUSION: This study indicates that EWDs may be more prevalent than previously thought, but they may go largely unnoticed due to their perceptually fleeting nature. The hypothesis was developed that EWDs be regarded as another type of developmental dysfluency, along with stuttering and cluttering. Ideas for further research are suggested.

Shared etiology of phonological memory and vocabulary deficits in school-age children.

PURPOSE: The goal of this study was to investigate the etiologic basis for the association between deficits in phonological memory (PM) and vocabulary in school-age children. METHOD: Children with deficits in PM or vocabulary were identified within the International Longitudinal Twin Study (ILTS; Samuelsson et al., 2005). The ILTS includes 1,045 twin pairs (between the ages of 5 and 8 years) from the United States, Australia, and Scandinavia. The authors applied the DeFries-Fulker ( DeFries & Fulker, 1985, 1988) regression method to determine whether problems in PM and vocabulary tend to co-occur because of overlapping genes, overlapping environmental risk factors, or both. RESULTS: Among children with isolated PM deficits, the authors found significant bivariate heritability of PM and vocabulary weaknesses both within and across time. However, when probands were selected for a vocabulary deficit, there was no evidence for bivariate heritability. In this case, it appears that the PM-vocabulary relationship is caused by common shared environmental experiences. CONCLUSIONS: The findings are consistent with previous research on the heritability of specific language impairment and suggest that there are etiologic subgroups of children with low vocabulary for different reasons, 1 being more influenced by genes and another being more influenced by environment.

[Molecular genetics of functional articulation disorder in children].

Genetic factors are an important cause of functional articulation disorder in children. This article reviews some genes and chromosome regions associated with a genetic susceptibility to functional articulation disorders. The forkhead box P2 (FOXP2) gene on chromosome 7 is introduced in details including its structure, expression and function. The relationship between the FOXP2 gene and developmental apraxia of speech is discussed. As a transcription factor, FOXP2 gene regulates the expression of many genes. CNTNAP2 as an important target gene of FOXP2 is a key gene influencing language development. Functional articulation disorder may be developed to dyslexia, therefore some candidate regions and genes related to dyslexia, such as 3p12-13, 15q11-21, 6p22 and 1p34-36, are also introduced. ROBO1 gene in 3p12.3, ZNF280D gene, TCF12 gene, EKN1 gene in 15q21, and KIAA0319 gene in 6p22 have been candidate genes for the study of functional articulation disorder.

Encoding, memory, and transcoding deficits in Childhood Apraxia of Speech.

A central question in Childhood Apraxia of Speech (CAS) is whether the core phenotype is limited to transcoding (planning/programming) deficits or if speakers with CAS also have deficits in auditory-perceptual encoding (representational) and/or memory (storage and retrieval of representations) processes. We addressed this and other questions using responses to the Syllable Repetition Task (SRT) [Shriberg, L. D., Lohmeier, H. L., Campbell, T. F., Dollaghan, C. A., Green, J. R., & Moore, C. A. (2009). A nonword repetition task for speakers with misarticulations: The syllable repetition task (SRT). Journal of Speech, Language, and Hearing Research, 52, 1189-1212]. The SRT was administered to 369 individuals in four groups: (a) typical speech-language (119), (b) speech delay-typical language (140), (c) speech delay-language impairment (70), and (d) idiopathic or neurogenetic CAS (40). CAS participants had significantly lower SRT competence, encoding, memory, and transcoding scores than controls. They were 8.3 times more likely than controls to have SRT transcoding scores below 80%. We conclude that speakers with CAS have speech processing deficits in encoding, memory, and transcoding. The SRT currently has moderate diagnostic accuracy to identify transcoding deficits, the signature feature of CAS.

Literacy outcomes of children with early childhood speech sound disorders: impact of endophenotypes.

PURPOSE: To demonstrate that early childhood speech sound disorders (SSD) and later school-age reading, written expression, and spelling skills are influenced by shared endophenotypes that may be in part genetic. METHOD: Children with SSD and their siblings were assessed at early childhood (ages 4-6 years) and followed at school age (7-12 years). The relationship of shared endophenotypes with early childhood SSD and school-age outcomes and the shared genetic influences on these outcomes were examined. RESULTS: Structural equation modeling demonstrated that oral motor skills, phonological awareness, phonological memory, vocabulary, and speeded naming have varying influences on reading decoding, spelling, spoken language, and written expression at school age. Genetic linkage studies demonstrated linkage for reading, spelling, and written expression measures to regions on chromosomes 1, 3, 6, and 15 that were previously linked to oral motor skills, articulation, phonological memory, and vocabulary at early childhood testing. CONCLUSIONS: Endophenotypes predict school-age literacy outcomes over and above that predicted by clinical diagnoses of SSD or language impairment. Findings suggest that these shared endophenotypes and common genetic influences affect early childhood SSD and later school-age reading, spelling, spoken language, and written expression skills.

Heritability estimation for speech-sound traits with developmental trajectories.

Numerous studies have examined genetic influences on developmental problems such as speech sound disorders (SSD), language impairment (LI), and reading disability. Disorders such as SSD are often analyzed using their component endophenotypes. Most studies, however, have involved comparisons of twin pairs or siblings of similar age, or have adjusted for age ignoring effects that are peculiar to age-related trajectories for phenotypic change. Such developmental changes in these skills have limited the usefulness of data from parents or siblings who differ substantially in age from the probands. Employing parent-offspring correlation in heritability estimation permits a more precise estimate of the additive component of genetic variance, but different generations have to be measured for the same trait. We report on a smoothing procedure which fits a series of lines that approximate a curve matching the developmental trajectory. This procedure adjusts for changes in measures with age, so that the adjusted values are on a similar scale for children, adolescents, and adults. We apply this method to four measures of phonological memory and articulation in order to estimate their heritability. Repetition of multisyllabic real words (MSW) showed the best heritability estimate of 45% in this sample. We conclude that differences in measurement scales across the age span can be reconciled through non-linear modeling of the developmental process.

Association between FOXP2 gene and speech sound disorder in Chinese population.

AIM: FOXP2 was described as the first gene relevant to human speech and language disorders. The main objective of this study was to compare the distribution of FOXP2 gene polymorphisms between patients with speech sound disorder and healthy controls. METHODS: Five FOXP2 polymorphisms, rs923875, rs2396722, rs1852469, rs17137124 and rs1456031, were analyzed in 150 patients with speech sound disorder according to DSM-IV, as well as in 140 healthy controls. Coding exons for key domains of FOXP2 were also sequenced in all the patients. RESULTS: Significant differences in the genotype (P = 0.001) and allele (P = 0.0025) frequencies of rs1852469 (located 5' upstream of the ATG initiator codon) were found between patients and controls. The excess of the T allele in the patients group remained significant after Bonferroni correction (P = 0.0126). Further investigations revealed a risk haplotype: rs2396722T/+rs1852469T. Our screening of key domains did not detect any point mutations in this sample. But we detected heterozygous triplet deletion of the glutamine-encoding region of exon 5 that alter FOXP2 protein sequence in five probands. These changes are predicted to yield a polyglutamine tract reduction from 40 to 39 consecutive glutamines. CONCLUSIONS: Our data support a possible role of FOXP2 in the vulnerability to speech sound disorder, which adds further evidence to implicate this gene in speech and language functions.

Pleiotropic effects of the 11p13 locus on developmental verbal dyspraxia and EEG centrotemporal sharp waves.

We recently showed genomewide linkage of centrotemporal sharp waves (CTS) in classic Rolandic epilepsy (RE) families to chromosome 11p13, and fine-mapped this locus to variants in the ELP4 gene. Speech sound disorder (SSD) is a common comorbidity in RE subjects, of unknown etiology, which co-aggregates in family members in a manner that could hypothetically be explained by shared underlying genetic risk with CTS. Furthermore, the neural mechanism of SSD is unknown, although individuals with rare, Mendelian forms of RE are described with severe verbal and oromotor apraxia. We therefore first performed genomewide linkage analysis for SSD, operationally defined as clinical history consistent with ICD-10 speech articulation disorder, in 38 families singly ascertained through a proband with RE. We tested the hypothesis of shared genetic risk with CTS at the 11p13 locus. In the second part of the study we used computerized acoustic analysis of recorded speech to test the hypothesis of dyspraxia as a mechanism for SSD in a smaller subset of RE probands and relatives. In two-point and multipoint LOD score analysis, we found that evidence for linkage to the 11p13 locus increased substantially when the phenotype was broadened from CTS to CTS/SSD. In multipoint analysis, the LOD score rose by 3.2 to HLOD 7.54 at D11S914 for CTS/SSD, the same marker at which multipoint linkage maximized for CTS alone. Non-parametric, affected-only methods in a sub-set of the data provide further confirmatory evidence for pleiotropy. In acoustic analysis there were voice-onset time abnormalities in 10/18 RE probands, 8/16 siblings and 5/15 parents, providing evidence of breakdown in the spatial/temporal properties of speech articulation consistent with a dyspraxic mechanism. The results from genetic and physiological studies suggest a pleiotropic role for the 11p13 locus in the development of both SSD and CTS, and also indicate a dyspraxic mechanism for the SSD linked to 11p13. Taken together, these data strongly support a neurodevelopmental origin for classic RE.

Possible mechanisms and gene involvement in speech problems in the 22q11.2 deletion syndrome.

SUMMARY: The 22q11.2 deletion syndrome represents a contiguous gene syndrome with a highly variable phenotype. To date, over 180 clinical features have been described. Studies have been done in order to identify the responsible genes. Several candidate genes such as TBX1 and COMT seem to be important in the development of the phenotype. One of the prevalent and serious problems encountered by patients with the 22q11.2 deletion is difficulty with speech. This may be due to a number of factors such as adenoid hypoplasia, muscle hypotonia, platybasia, upper airway asymmetry, and neuroanatomical abnormalities. The complex interaction of these factors leads to less favourable results after surgery to correct velopharyngeal insufficiency. This article offers a theoretical overview and proposes future research to investigate which factors are indeed responsible for the speech problems encountered by patients with the 22q11.2 deletion and identify responsible genes.

Central timing deficits in subtypes of primary speech disorders.

Childhood apraxia of speech (CAS) is a proposed speech disorder subtype that interferes with motor planning and/or programming, affecting prosody in many cases. Pilot data (Peter & Stoel-Gammon, 2005) were consistent with the notion that deficits in timing accuracy in speech and music-related tasks may be associated with CAS. This study replicated and expanded earlier findings. Eleven children with speech disorders and age-and gender-matched controls participated in non-word imitation, clapped rhythm imitation, and paced repetitive tapping tasks. Results suggest a central timing deficit, expressed in both the oral and the limb modality, and observable in two different types of timing measures, overall rhythmic structures and small-scale durations. Associations among timing measures were strongest in the participants with speech disorders, who also showed lower timing accuracy than the controls in all measures. The number of observed CAS characteristics was associated with timing deficits.

Gene x Environment interactions in speech sound disorder predict language and preliteracy outcomes.

Few studies have investigated the role of gene x environment interactions (G x E) in speech, language, and literacy disorders. Currently, there are two theoretical models, the diathesis-stress model and the bioecological model, that make opposite predictions about the expected direction of G x E, because environmental risk factors may either strengthen or weaken the effect of genes on phenotypes. The purpose of the current study was to test for G x E at two speech sound disorder and reading disability linkage peaks using a sib-pair linkage design and continuous measures of socioeconomic status, home language/literacy environment, and number of ear infections. The interactions were tested using composite speech, language, and preliteracy phenotypes and previously identified linkage peaks on 6p22 and 15q21. Results showed five G x E at both the 6p22 and 15q21 locations across several phenotypes and environmental measures. Four of the five interactions were consistent with the bioecological model of G x E. Each of these four interactions involved environmental measures of the home language/literacy environment. The only interaction that was consistent with the diathesis-stress model was one involving the number of ear infections as the environmental risk variable. The direction of these interactions and possible interpretations are explored in the discussion.

Perceptual and acoustic analysis of speech in individuals with spinocerebellar ataxia (SCA).

With current progress in genetic research, autosomal, dominant, hereditary, neurodegenerative diseases, affecting the cerebellum and cerebellar connections, are increasingly diagnosed as spinocerebellar ataxias (SCA). In the present study speech samples from 21 subjects with spinocerebellar ataxia (SCA), and 21 matched control subjects were analyzed using perceptual and acoustic methodology. Dysarthria assessment showed that subjects had mild or mild-moderate dysarthria. Perceptual analysis indicated that equalized stress, imprecise consonants, vocal instability, monotony and reduced speech rate were the speech parameters that yielded the highest mean perceptual ratings. A factor analysis of perceptual speech parameters revealed two main factors: Factor 1 was associated with articulatory timing and Factor 2 with vocal quality. Acoustic analysis revealed significantly reduced speech rate during text reading, reduced alternating and sequential motion rates (AMR/SMR), significantly longer and more variable syllable and pause durations, and significantly higher vocal instability for subjects with SCA compared to control subjects.

Overall intelligibility, language, articulation, voice and resonance characteristics in a child with Shprintzen-Goldberg syndrome.

OBJECTIVE: Recognition of the phenotypic spectrum and prognosis of a genetic disorder is critical to proper patient care. A 7-year-old boy with Sphrintzen-Goldberg syndrome (SGS) was studied to investigate speech, language and voice patterns associated with this syndrome. METHODS: The child's language (expressive and receptive) and speech was characterized with regard to overall intelligibility, articulation (phonetic and phonological errors), voice (flexible videolaryngostroboscopy, quality, pitch and loudness) and resonance (type of disorders). RESULTS: Based on this detailed study the most striking communication characteristics in this child with SGS appear to be a delayed speech and language onset, an expressive and receptive language disorder, a moderately impaired speech intelligbility, relatively good phonetic but poorer phonological abilities, an oral hypotonia, a high-pitched soft voice and a slight hypernasality. CONCLUSIONS: The explanation for this communication disorder is not completely straightforward. It is not clear either to what extent the present case can be considered as typical for SGS. Only more data will allow to determine whether or not SGS is associated with a typical syndrome specific pattern of communication disorders. Not only detailed speech and language analyses of additional cases of SGS are necessary, but also studies that compare the speech and language of individuals with SGS with that of individuals with other genetic syndrome.

Further evidence of pleiotropy influencing speech and language: analysis of the DYX8 region.

BACKGROUND/AIMS: Genetic studies have raised the possibility of common bases for cognitive linguistic disorders such as speech sound disorder (SSD), reading disorder (RD) and language impairment (LI). Thus, some of the same genes may jointly influence cognitive components within and between these three disorders. We examined the plausibility of this theory in a sample of families ascertained on the basis of a child with SSD. METHODS: Using the method of generalized estimating equations to solve a bivariate family predictive model we obtained measures of comorbidity and familial aggregation of SSD and LI. We then used two methods of multipoint model-free linkage analysis to evaluate SSD and LI psychometric test measures over a region previously implicated in linkage studies of RD, DYX8 region, 1p34-p36. RESULTS: Bivariate phenotypic analyses show evidence of comorbidity and within family aggregation and coaggregation of SSD and LI. In addition, two regions on chromosome 1 show suggestive evidence of linkage. The first region was previously reported in dyslexia studies. Our maximum linkage signal in this region measured articulation (p = 0.0009) in SSD sibling pairs. The second region is characterized by processes involved in language production, with the maximum linkage signal measuring listening comprehension (p = 0.0019) using all sibling pairs. CONCLUSION: We conclude that the DYX8 region could bear genes controlling pleiotropic effects on SSD, LI and RD.

[Familial aspect and phonological disorder]. / O aspecto familial e o transtorno fonológico.

BACKGROUND: Phonological disorder. AIM: To verify the phonological processes used by phonologically disordered children with and without family history of speech and language disorders; the association between the phonological processes; the difference between the Percentage of Correct Consonants-Revised (PCC-R) severity index regarding family history. METHOD: Participants were 104 subjects--25 phonologically disordered children--with no history of previous speech-language therapy, living with their biological parents and siblings. The material used was a child development questionnaire and the phonology tests of the Teste de Linguagem Infantil-ABFW. RESULTS: Liquid simplification was the most observed process independently of family history; the phonological process of devoicing was mostly observed when the family members presented phonological disorders; the phonological process observed in children are, in general, different from those presented by the family nucleus, and those that are similar do not determine characteristics of family history since they are processes frequently observed in subjects with phonological disorders; the PCC-R severity index did not differentiate types of phonological disorders regarding family history. CONCLUSION: This research shows characteristics that indicate that family history of speech and language disorder is associated to phonological disorders. The knowledge about the child's family history facilitates the planning and execution of early intervention actions, preventing the aggravation of phonological disorders. The PCC-R severity index does not differentiate types of phonological disorders regarding family history.

O aspecto familial e o transtorno fonológico / Familial aspect and phonological disorder

TEMA: transtorno fonológico. OBJETIVO: verificar: os processos fonológicos apresentados por crianças com diagnóstico de transtorno fonológico com e sem história de transtorno de fala e linguagem no núcleo familiar; a associação entre os processos fonológicos; a diferença do índice de gravidade Porcentagem de Consoantes Corretas-Revisado (PCC-R) em relação ao histórico familial. MÉTODO: participaram da pesquisa 104 sujeitos - sendo 25 crianças com transtorno fonológico, sem terapia fonoaudiológica prévia e deveriam morar com os pais biológicos e seus irmãos. O material utilizado foi anamnese, questionário específico e as provas de fonologia do Teste de Linguagem Infantil ABFW. RESULTADOS: a simplificação de líquidas foi o processo fonológico mais ocorrente independentemente do histórico familial; os processos fonológicos de ensurdecimento foram mais observados quando os familiares apresentavam diagnóstico de transtorno fonológico atual; os processos fonológicos observados nas crianças são, em geral, diferentes daqueles presentes no núcleo familiar, e os que são iguais não determinam características próprias de histórico familial, na medida em que são os mais freqüentemente presentes em sujeitos com transtorno fonológico; houve associação entre os processos fonológicos quando considerado o histórico familial; o índice de gravidade PCC-R não diferenciou o transtorno em relação ao histórico familial. CONCLUSÃO: a pesquisa mostrou fatores que indicam que o histórico familial de transtorno de fala e linguagem está associado ao transtorno fonológico. O conhecimento do histórico familial da criança facilita o planejamento e execução de medidas de intervenção precoce podendo prevenir os agravamentos do transtorno fonológico. O índice de gravidade PCC-R não diferencia o transtorno fonológico em relação ao histórico familial.

BACKGROUND: phonological disorder. AIM: to verify the phonological processes used by phonologically disordered children with and without family history of speech and language disorders; the association between the phonological processes; the difference between the Percentage of Correct Consonants-Revised (PCC-R) severity index regarding family history. METHOD: participants were 104 subjects - 25 phonologically disordered children - with no history of previous speech-language therapy, living with their biological parents and siblings. The material used was a child development questionnaire and the phonology tests of the Teste de Linguagem Infantil - ABFW. RESULTS: liquid simplification was the most observed process independently of family history; the phonological process of devoicing was mostly observed when the family members presented phonological disorders; the phonological process observed in children are, in general, different from those presented by the family nucleus, and those that are similar do not determine characteristics of family history since they are processes frequently observed in subjects with phonological disorders; the PCC-R severity index did not differentiate types of phonological disorders regarding family history. CONCLUSION: this research shows characteristics that indicate that family history of speech and language disorder is associated to phonological disorders. The knowledge about the child's family history facilitates the planning and execution of early intervention actions, preventing the aggravation of phonological disorders. The PCC-R severity index does not differentiate types of phonological disorders regarding family history.

Phonology and handedness in primary school: predictions of the right shift theory.

BACKGROUND: The right shift (RS) theory of handedness suggests that poor phonology may occur in the general population as a risk associated with absence of an agent of left cerebral speech, the hypothesised RS + gene. The theory predicts that poor phonology is associated with reduced bias to right-handedness. METHODS: A representative cohort of primary school children was assessed on tests of phonology, nonverbal ability, literacy, and handedness. There were three types of analysis; for discrete variables, poor phonology and left hand preference; for continuous variables, phonology factor scores and hand skill; for "cases" of specifically poor phonology. RESULTS: Reduced bias to dextrality was found in those with poor phonology for all types of analysis. Trends were similar for both sexes but stronger in males than females. Poor phonology was associated with a raised proportion of left-handed brothers. There was a strong association between poor phonology and poor literacy, but not all those with specifically poor phonology were poor readers or spellers. Among children with poor phonology but not poor for other variables, some 23-31% were left-handed writers. CONCLUSIONS: Poor phonological processing is associated with reduced bias to the right hand, consistent with absence of an agent of left hemisphere advantage.

The genetic bases of speech sound disorders: evidence from spoken and written language.

The purpose of this article is to review recent findings suggesting a genetic susceptibility for speech sound disorders (SSD), the most prevalent communication disorder in early childhood. The importance of genetic studies of SSD and the hypothetical underpinnings of these genetic findings are reviewed, as well as genetic associations of SSD with other language and reading disabilities. The authors propose that many genes contribute to SSD. They further hypothesize that some genes contribute to SSD disorders alone, whereas other genes influence both SSD and other written and spoken language disorders. The authors postulate that underlying common cognitive traits, or endophenotypes, are responsible for shared genetic influences of spoken and written language. They review findings from their genetic linkage study and from the literature to illustrate recent developments in this area. Finally, they discuss challenges for identifying genetic influence on SSD and propose a conceptual framework for study of the genetic basis of SSD.