developmental language disorder developmental language disorder developmental language disorder (dld) is identified when a child has problems with language development that continue into school age and beyond. the language problems have a significant impact on everyday social interactions or educational progress, and occur in the absence of autism spectrum disorder, intellectual disability or a known biomedical condition. the most obvious problems are difficulties in using words and sentences to express meanings, but for many children, understanding of language (receptive language) is also a challenge. this may not be evident unless the child is given a formal assessment. developmental language disorderspecialtyneurology classification terminology the term developmental language disorder (dld) was endorsed in a consensus study involving a panel of experts (catalise consortium) in 2017. the study was conducted in response to concerns that a wide range of terminology was used in this area, with the consequence that there was poor communication, lack of public recognition, and in some cases children were denied access to services. developmental language disorder is a subset of language disorder, which is itself a subset of the broader category of speech, language and communication needs (slcn). the terminology for children's language disorders has been extremely wide-ranging and confusing, with many labels that have overlapping but not necessarily identical meanings. in part this confusion reflected uncertainty about the boundaries of dld, and the existence of different subtypes. historically, the terms "developmental dysphasia" or "developmental aphasia" were used to describe children with the clinical picture of dld. these terms have, however, largely been abandoned, as they suggest parallels with adult-acquired aphasia. this is misleading, as dld is not caused by brain damage. although the term dld has been used for many years, it has been less common than the term specific language impairment (sli), which has been widely adopted, especially in north america. the definition of sli overlaps with dld, but was rejected by the catalise panel because it was seen as overly restrictive in implying that the child had relatively pure problems with language in the absence of any other impairments. children with such selective problems are relatively rare, and there is no evidence that they respond differently to intervention, or have different causal factors, from other children with language problems. in the uk education system, the term speech, language and communication needs (slcn) is widely used, but this is far broader than dld, and includes children with speech, language and social communication difficulties arising from a wide range of causes. the question of whether to refer to children's language problems as a 'disorder' was a topic of debate among the catalise consortium, but the conclusion was that 'disorder' conveyed the serious nature and potential consequences of persistent language deficits. it is also parallel with other neurodevelopmental conditions and consistent with diagnostic frameworks such as the dsm-5 and icd-11. where there are milder or more transient difficulties, 'language difficulties' may be a more appropriate term. areas of language difficulty dld can affect a range of areas of language and the degree of impairment in different areas of language can vary from child to child. however, although there have been attempts to define different subtypes, these have not generally resulted in robust categories. the recommendation of the catalise panel was that the specific areas of impairment should be assessed and documented for individual children, while recognizing that different children might have different combinations of problems. the areas which can be affected are: grammar – this involves the ability to combine words into grammatically correct sentences (syntax) and to combine parts of words together (morphology) such as adding grammatical endings to verbs like -ing or -ed or to add prefixes and suffixes like dis- or -ation. for instance, a child may say 'me jump here', instead of 'i jumped here'. comprehension of sentences can also be affected. for instance, there may be difficulty understanding meaning expressed by word order, and so confusion about what is blue in a sentence like 'the pencil on the shoe is blue', and a tendency to use general knowledge rather than linguistic cues to meaning, or problems in interpreting grammatical markers of number or tense. semantics – this refers to children's ability to understand the meaning of words and how meanings are expressed by combining words together. children with dld often have limited vocabulary and may make heavy use of a small set of words with rather general meanings. as children with developmental language disorder get older, they may have a hard time understanding that some words have multiple meanings, for example the word "cold", which can mean a low temperature, a sickness, or being unfriendly. word finding – children with word finding difficulties may know a word, but have difficulty accessing it for production – similar to the tip of the tongue phenomenon. pragmatics – pragmatics refers to the ability to select the appropriate message, or interpret what others say, in relation to context. pragmatic difficulties can give an impression of oddity, with the content of language not fitting the environmental or social context; comprehension may be over-literal; the child may chatter incessantly, be poor at turn-taking in conversation and maintaining a topic discourse – discourse refers to a level of organization of language beyond the sentence. child with limitations in this domain may have limited ability to tell a story or describe a set of events in a logical sequence verbal memory and learning – problems with remembering words or sentences can affect both the learning of new vocabulary, and the understanding of long or complex sentences. young children with dld may say their first words later than other children. it may also take children with dld longer to learn and remember novel words. phonology – phonology is the branch of linguistics concerned with the way sounds are combined in words. children with difficulties with phonology may fail to distinguish between certain speech sounds, such as 't' and 'k', so that 'cake' is produced as 'tate'. such difficulties are not unusual as part of typical development in toddlers, but they would usually resolve by the time children are 4–5 years old. difficulties with producing some speech sounds accurately may reduce intelligibility of speech. in addition, more subtle difficulties in recognising specific sounds in words (phonological awareness) can lead to literacy difficulties. relationship with speech disorders speech is the act of articulating sounds, and this can be impaired for all kinds of reasons – a structural problem such as cleft lip and cleft palate, a neurological problem affecting motor control of the speech apparatus dysarthria, or inability to perceive distinctions between sounds because of hearing loss. some distortions of speech sounds, such as a lisp, are commonly seen in young children. these misarticulations should not be confused with language problems, which involve the ability to select and combine linguistic elements to express meanings, and the ability to comprehend meanings. although speech disorders can be distinguished from language disorders, they can also co-occur. when a child fails to produce distinctions between speech sounds for no obvious reason, this is typically regarded as a language problem affecting the learning of phonological contrasts. the classification of and terminology for disorders of speech sound production is a subject of considerable debate. in practice, even for those with specialist skills, it is not always easy to distinguish between phonological disorders and other types of speech production problem. speech sound disorder (ssd) is any problem with speech production arising from any cause. speech sound disorders of unknown cause that are not accompanied by other language problems are a relatively common reason for young children to be referred to speech-language therapy (speech-language pathology). these often resolve by around 4–5 years of age with specialist intervention, and so would not meet criteria for dld. where such problems continue beyond five years of age, they are usually accompanied by problems in broader language domains and have a poorer prognosis, so a diagnosis of dld with ssd is then appropriate. developmental language disorder impairment compared to other common language related disorders relationship with other neurodevelopmental disorders dld often co-occurs with milder neurodevelopmental disorders of unknown origin, such as attention-deficit hyperactivity disorder, developmental dyslexia or developmental coordination disorder. these do not preclude a diagnosis of dld, but should be noted as co-occurring conditions. risk factors it is generally accepted that dld is strongly influenced by genetic factors. the best evidence comes from the twin study method. two twins growing up together are exposed to the same home environment, yet may differ radically in their language skills. such different outcomes are, however, much more common in fraternal (non-identical) twins, who are genetically different. identical twins share the same genes and tend to be much more similar in language ability. there can be some variation in the severity and persistence of dld in identical twins, indicating that non-genetic factors affect the course of disorder, but it is unusual to find a child with dld who has an identical twin with typical language. there was considerable excitement when a large, multigenerational family with a high rate of dld were found to have a mutation of the foxp2 gene just in the affected family members. however, subsequent studies have found that, though dld runs in families, it is not usually caused by a mutation in foxp2 or another specific gene. current evidence suggests that there are many different genes that can influence language learning, and dld results when a child inherits a particularly detrimental combination of risk factors, each of which may have only a small effect. nevertheless, study of the mode of action of the foxp2 gene has helped identify other common genetic variants involved in the same neural pathways that may play a part in causing dld. language disorders are associated with aspects of home environment, and it is often assumed that this is a causal link, with poor language stimulation leading to weak language skills. twin studies, however, show that two children in the same home environment can have very different language outcomes, suggesting we should consider other explanations for the link. children with dld often grow up into adults who have relatively low educational attainments, and their children may share a genetic risk for language disorder. one non-genetic factor that is known to have a specific impact on language development is being a younger sibling in a large family. associated factors it has long been noted that males are more affected by dld than females, with a sex ratio of affected males-to-females around 3 or 4:1. however, the sex difference is much less striking in epidemiological samples, suggesting that similar problems may exist in females but are less likely to be detected. the reason for the sex difference is not well understood. poor motor skills are commonly found in children with dld. standardized measures of motor ability confirm that children with dld exhibit deficits in fine and gross motor skill, both simple and complex. these difficulties also extend to speech-motor ability, particularly with the control of their articulatory movements. children with dld have difficulty with motor sequence learning and may show deficits in other procedural motor processes as well. brain scans do not usually reveal any obvious abnormalities in children with dld, although quantitative comparisons have found differences in brain size or relative proportions of white or grey matter in specific regions. in some cases, unusual brain gyri are found. to date, no consistent 'neural signature' for dld has been found, although some studies have noted evidence for involvement of subcortical systems. differences in the brains of children with dld versus typically developing children are subtle and may overlap with atypical patterns seen in other neurodevelopmental disorders. diagnosis dld is defined purely in behavioural terms: there is no biological test. there are three points that need to be met for a diagnosis of dld: the child has language difficulties that create obstacles to communication or learning in everyday life, the child's language problems are unlikely to resolve by five years of age, and the problems are not associated with a known biomedical condition such as brain injury, neurodegenerative conditions, genetic conditions or chromosome disorders such as down syndrome, sensorineural hearing loss, autism spectrum disorder, or intellectual disability. for research and epidemiological purposes, specific cutoffs on language assessments have been used to document the