Specific learning disorders in children: Clinical features

INTRODUCTION — Learning disorders (LD) are a heterogeneous group of disorders characterized by difficulties mastering academic skills. Academic skills are substantially and measurably below those expected for chronologic age and interfere with academic or occupational performance [1]. LDs are the most common form of learning disability in children.

LDs have a multifactorial etiology [2]. They typically manifest as a failure to acquire reading, writing, or math skills at grade- and age-expected levels. Learning problems that are outside of these traditional core domains, such as memory problems, attention problems, processing speed deficits, and difficulty managing social interactions, are not typically considered to be LDs. However, they may affect reading, writing, and math and may also require intervention.

The clinical features of LDs will be presented here. Educational definitions for LD, the evaluation of LD, educational interventions for LD, and the role of the primary care provider are discussed separately:

●(See "Definitions of specific learning disorder and laws pertaining to learning disorders in the United States".)

●(See "Specific learning disorders in children: Evaluation".)

●(See "Specific learning disorders in children: Educational management".)

●(See "Specific learning disorders in children: Role of the primary care provider".)

TERMINOLOGY — This topic review uses the term "learning disorder (LD)" or "specific learning disorder," consistent with the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR) [1]. Specific learning disorders are a heterogeneous group of disorders characterized by difficulties with academic skills in reading, writing, and/ or math that usually are mastered during the early school years. The skills are substantially and measurably below those expected for chronologic age and interfere with academic or occupational performance [1].

"Learning disorder" and "learning disability" refer to the same neurodevelopmental conditions. There is a lack of consensus case definition. Between three commonly used definitions (table 1), there is agreement that the core features include impairments in specific, academic skills that are normally mastered during the early school years. Impairment is determined by comparison with age-related norms of performance [1] and/or the individual's overall intellectual potential [3-6]. We prefer the DSM-5-TR definition because of its stronger conceptual basis and therapeutic utility. (See "Definitions of specific learning disorder and laws pertaining to learning disorders in the United States", section on 'Educational definitions'.)

EPIDEMIOLOGY — Learning disorders (LDs) are twice as common in children with chronic health conditions as in children without chronic health conditions. Children who receive special education services have greater rates of health care utilization than children who do not receive special education services [7,8]. These correlations persist into adolescence and adulthood [9]. As such, pediatricians are especially likely to encounter children with LD. However, they may not recognize those children unless they ask about learning problems specifically.

Prevalence — The prevalence of LD is difficult to determine because different criteria are used to define LD in different settings. However, data from the National Center for Education Statistics indicate that in 2020-2021, 15 percent of all public school students age 3 to 21 years received special education services under the Individuals with Disabilities Education Act (IDEA) [10]. Among students receiving IDEA services, 33 percent were categorized as having a specific learning disability and 19 percent as having a speech or language impairment. These statistics must be interpreted with caution; they indicate the proportion of students who were found eligible for specialized instruction, which is not the same as the number of students who meet criteria for a Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR) diagnosis of LD.

Disorders of reading and written expression are the most common forms of LD. In a population-based study, the prevalence of reading disability among school-age children was estimated to be between 5 and 12 percent, depending upon the criteria used for definition (intelligence-achievement discrepancy versus low achievement, respectively) [11]. In the same population, the prevalence of disorders of written expression was estimated to be between 7 and 15 percent [12]. In separate studies, the prevalence of dyscalculia (math disability) was estimated to be between 3 and 6 percent of the school-age population [13-15].

Risk factors — The prevalence of LD is increased among children:

●With family history of LD [16-18]

●Who live in poverty and understimulating environments [19-21]

●Who were born prematurely (see "Long-term neurodevelopmental impairment in infants born preterm: Risk assessment, follow-up care, and early intervention")

●With other developmental and mental health conditions, such as attention deficit hyperactivity disorder, disruptive behavior disorders, autism, anxiety disorders, and depression (see "Attention deficit hyperactivity disorder in children and adolescents: Clinical features and diagnosis", section on 'Evaluation for coexisting disorders' and "Autism spectrum disorder in children and adolescents: Clinical features", section on 'Intellectual impairment' and "Pediatric unipolar depression: Epidemiology, clinical features, assessment, and diagnosis", section on 'Comorbidity')

●With prenatal alcohol exposure (see "Fetal alcohol spectrum disorder: Clinical features and diagnosis", section on 'Central nervous system involvement')

●With neurologic conditions (eg, seizure disorders, neurofibromatosis, tuberous sclerosis complex, Tourette syndrome) (see "Tuberous sclerosis complex: Genetics, clinical features, and diagnosis", section on 'Cognitive deficits' and "Tourette syndrome: Pathogenesis, clinical features, and diagnosis", section on 'Comorbidities' and "Neurofibromatosis type 1 (NF1): Pathogenesis, clinical features, and diagnosis", section on 'Neurologic abnormalities')

●With chromosomal disorders (eg, fragile X syndrome, Turner syndrome, Klinefelter syndrome) (see "Fragile X syndrome: Clinical features and diagnosis in children and adolescents", section on 'Cognitive function' and "Clinical manifestations and diagnosis of Turner syndrome", section on 'Psychologic and educational issues' and "Clinical features, diagnosis, and management of Klinefelter syndrome", section on 'Psychosocial and cognitive abnormalities')

●With certain chronic medical conditions (eg, type 1 diabetes mellitus, human immunodeficiency virus [HIV] infection) (see "Pediatric HIV infection: Classification, clinical manifestations, and outcome", section on 'HIV encephalopathy' and "Hypoglycemia in children and adolescents with type 1 diabetes mellitus", section on 'Neurologic sequelae')

●With a history of central nervous system infection or irradiation or traumatic brain injury (see "Bacterial meningitis in children: Neurologic complications", section on 'Behavioral problems' and "Overview of the management of central nervous system tumors in children", section on 'Neurocognitive effects')

ETIOLOGY AND PATHOGENESIS — Learning disorders (LDs) are caused by inborn or acquired abnormalities in brain structure and function and have a multifactorial etiology [2]. LDs may be present at birth or acquired after birth as a result of illness, exposure to toxins, poor nutrition, medical treatment, sociocultural deprivation, or injury [22-25].

LDs are not caused by eye problems [26,27]. Although the eyes are essential to the receipt of visual input, it is the brain that processes visual stimuli and interprets visual images (eg, reverses letters, words, or numbers) [2]. Neither LDs nor the processing of visual input is affected by the correction of subtle visual defects [28].

The pathogenesis of LDs is not known. Genetic and neuropathologic causes may be at the core of LD, particularly in the case of reading disability. However, the full expression of LD occurs as a result of these neuropathologic differences in conjunction with other intrinsic and environmental factors that affect learning.

Other intrinsic factors include brain functions, such as language skills, executive functions, and social cognition.

Environmental factors include school factors (eg, student-teacher interactions; appropriately paced instruction; the student's past exposure to learning opportunities at school; level of stimulation provided by the learning materials; physical layout of the classroom setting) and home factors (eg, past exposure to learning at home, degree of support provided in the home for reading and homework completion, etc). [29-33]. For a review of these factors and their association with socioeconomic status, see reference [34].

Neuropathologic causes for learning failure can be mitigated with appropriate specialized instruction and a supportive learning environment and can be aggravated when the learning environment is not supportive. Successful remedial educational interventions have been associated with changes in brain function specific to language processes [35]. (See "Reading difficulty in children: Normal reading development and etiology of reading difficulty", section on 'Etiology and pathogenesis of reading disability'.)

CLINICAL FEATURES

LD syndromes — Learning disorders (LDs) are a heterogeneous group of disorders that require individualized evaluation and intervention. Nonetheless, patterns of learning problems often cluster together [36]. The following LD syndromes are commonly recognized (table 2):

Reading disability — Specific reading disability (dyslexia) is estimated to occur in approximately 5 to 12 percent of school-age children, depending upon the criteria used for definition [11]. Dyslexia is a specific type of reading disorder caused by deficits in phonologic processing. Difficult/slow reading also can be caused by orthographic processing deficits (difficulty recognizing words by sight and needing to sound out every letter to read the word). The deficits are unexpected in relation to the student's chronologic age and persist even after receiving appropriate (general education) instruction.

Skills that are necessary for reading include the ability to:

●Being able to hear and discriminate the sounds of spoken English or spoken heritage language

●Being able to produce the speech sounds of a language

●Match printed symbols (letters or letter combinations) with spoken sounds (speech); this skill is referred to as "phonics" and applies to any language (such as English) that uses symbols or letters to represent speech sounds

●Produce the sound that is associated with a printed letter or letter combination when reading printed words; this skill is referred to as "reading decoding"

Reading disability typically presents initially with problems in decoding in the first year or two of school. Even when decoding is mastered, students with reading disability continue to present with dysfluent reading (slow or effortful decoding) in higher grades.

Dysfluent reading results in reading comprehension difficulty. Problems with reading comprehension usually present in the latter part of the primary school years, when the focus is on reading to learn rather than learning to read. Children with reading disability may have attention problems and may avoid reading. They can be identified by low overall reading achievement or by low reading ability in relation to their overall intelligence.

Reading disability is discussed in detail separately. (See "Reading difficulty in children: Normal reading development and etiology of reading difficulty" and "Reading difficulty in children: Clinical features and evaluation" and "Reading difficulty in children: Interventions".)

Writing disability — Disabilities in written expression are estimated to occur in approximately 7 to 15 percent of school-age children, depending upon the criteria used for definition [12]. Writing disabilities are caused by a range of neurodevelopmental weaknesses or disabilities, including problems with [37-39]:

●Handwriting (fine motor or graphomotor) weaknesses.

●Spelling, the ability to match a spoken sound in speech with its corresponding letter or letter combination. This skill is referred to as "encoding." Problems with spelling always accompany reading decoding problems; both are indicative of an underlying problem in phonics.

●Grammar and syntax (understanding and using language to write grammatically correct sentences).

●Formulating, expressing, and organizing ideas in writing (organizing ideas in written text).

LDs in written expression affect all areas of academics. Children with LDs in written expression may present with difficulty copying efficiently from the whiteboard or smartboard, may show excessive errors in grammar and punctuation, may produce overly simple written text, and/or may produce disorganized text that is difficult to follow.

The differential diagnosis of disorders of written expression includes (see 'Differential diagnosis' below) [40-42]:

●Developmental coordination disorder (particularly for children with handwriting problems) (see "Developmental coordination disorder: Clinical features and diagnosis", section on 'Clinical features')

●Reading disability (especially for children who have decoding weaknesses) (see "Reading difficulty in children: Clinical features and evaluation")

●Language disorder (particularly for children whose text contains too many grammatical errors or is otherwise impoverished and/or disorganized) (see "Evaluation and treatment of speech and language disorders in children" and "Etiology of speech and language disorders in children")

●Attention deficit hyperactivity disorder (ADHD; for children who have difficulty organizing their ideas in writing) (see "Attention deficit hyperactivity disorder in children and adolescents: Clinical features and diagnosis", section on 'Clinical features')

Math learning disorder — Mathematics LDs (dyscalculia) are primarily due to weaknesses in number sense and in performing calculations. Math learning difficulty can also occur for other reasons, as outlined below. Math LD is estimated to occur in 3 to 6 percent of children [13,14,43], or 6 to 13.8 percent [44], depending on the age of the student and the formula used to defined math LD.

Success in math depends upon mastering of a range of skills. These skills are not necessarily acquired in a linear manner. The most important components of math LD include difficulties in mastering number sense, math calculations (adding, subtracting, dividing, and multiplying), and math facts (automatic retrieval) [45]. In addition to these basic components, students with math LD can have difficulty with the language of math (correctly reading and understanding numbers and symbols), with word problems in math (correctly reading and understanding math word problems, correctly transcribing the word problems into a numerical equation), and with the visual-spatial and organizational demands of math [46]. Success in math is thus dependent on a broad range of neurodevelopmental functions. Each of these is summarized below:

●Number sense – Number sense refers to having a mental representation of quantity. It is an early emerging skill that fails to develop in students with math LD and may manifest as [45,47-49]:

•Difficulty in estimating and judging magnitude (eg, understanding "bigger/smaller" or "less/more")

•Difficulty understanding the principle of commutativity (order irrelevance) in math problems (ie, the order in which objects are counted does not change the final number of objects)

•Inability to produce a number line, a mental representation of numbers used in all math calculations

•Inability to represent the same number in more than one manner (eg, as a collection of objects, as a percentage or decimal value, as a fraction, or in terms of space and time)

•Inability to recognize benchmark numbers and number patterns, (eg, prime numbers, all multiples of 10 [or another number])

•Inability to recognize unreasonable results when doing math calculations

●Calculation and retrieval of math facts – Math facts refer to the basic calculations taught in primary school (eg, adding, subtracting, multiplying, and dividing). Common one- and two-digit math facts are usually memorized and then retrieved automatically from memory in later grades and in solving higher-order math problems. Difficulty performing math calculations is commonly related to problems with number sense. The student with poor math fact skills may not know how to complete math calculations and may over-rely on tangible aids, such as objects, pictures, or tables. Difficulty with the automatic retrieval of math facts is another manifestation of math disability and can also create difficulty in solving higher-order math problems. Teaching the rapid retrieval of math facts can be a specific focus for intervention and instruction.

●Language of math – Students with math LD may fail to correctly read and understand numbers and math symbols. They may reverse numbers or make errors when reading numbers aloud.

●Ability to understand word problems – Math LDs can accompany disabilities in reading or written expression. Mathematic calculations depend upon successful development of language and on the ability of the student to understand the words associated with math functions and word problems [42]. Reading difficulties can aggravate difficulty acquiring math skills. Students with reading disability have difficulty with word problems because they do not understand the meaning of the sentence in math word problems and may not be able to identify extraneous or irrelevant material. These students fail to correctly transcribe math word problems into numerical equations.

●Visual-spatial and organizational skills – Math LD can be caused by difficulties in handwriting, visual-spatial orientation, temporal sequencing, memory, and attention [30]. Students with math LD may have difficulty organizing math problems on the page. They may copy numbers incorrectly, write numbers illegibly, misalign numbers, have left-right disorientation of numbers, misplace digits in multidigit numbers, skip rows or columns during calculations, fail to carry numbers (eg, regrouping when appropriate), reverse number problems, start a calculation in the wrong place, or not recognize operator signs. Students with math LD also have difficulty planning and organizing their approach to math problems. They have difficulty with multistep problems; they may fail to verify answers and may settle for the first answer they reach for a given problem.

The differential diagnosis of calculation and math LDs includes reading disability, disorder of written expression, language disorder, and ADHD. These disorders can coexist, compounding the functional deficit. (See 'Differential diagnosis' below.)

Language-based learning disorder — Students with language-based LDs have difficulty when they are required to use language for learning and school success. The learning deficits vary with the component of language that is affected. Language impairment can affect student performance at the level of:

●Phonology (discriminating the sounds in words)

●Articulation (the ability to produce speech sounds)

●Words (vocabulary)

●Sentences (grammar, also referred to as morphology and syntax)

●Discourse (strings of sentence that occur in a narrative or conversation)

The effects of language-based LD on reading and writing are different than those of reading disability or writing disability (table 2). Students with language impairment do not necessarily have difficulty with encoding and decoding (phonics) or handwriting, which are hallmark features of reading and writing disabilities. Although students with language-based LDs may be able to encode, decode, and print words as well as their peers, they may not have the vocabulary, grammar, or narrative skills needed to comprehend text or write a composition at the level expected for their age or grade.

Students with language impairment also may have difficulties with classroom participation. They may not be able to understand and follow teacher directions, follow or participate in classroom discussion, and may even have difficulty communicating with peers in a social setting. These classroom participation behaviors are as important as reading and writing for the student's success at school. Language impairment and associated problems with classroom participation also mandate remediation and/or accommodations.

Language disorders are discussed in detail separately. (See "Evaluation and treatment of speech and language disorders in children" and "Etiology of speech and language disorders in children", section on 'Language disorders'.)

Nonverbal learning disorder — The nonverbal LD syndrome (nonlanguage-based LD, NLD, also known as right hemisphere developmental LD) is a cluster of behaviors and symptoms, not all of which are in the nonverbal domain. NLD is characterized by a particular pattern of neuropsychologic abilities and disabilities. NLD is not recognized in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR) [1]. Diagnostic criteria vary by author and clinician. In contrast to the LD syndromes described above, which typically can be identified by the primary care provider, the primary care provider is not expected to identify NLD. A neuropsychology evaluation is usually needed to make the diagnosis.

Common features of the NLD syndrome include [33,50-54]:

●Well-developed basic language skills

●Strong rote skills, such as phoneme awareness, reading decoding, single-word reading, and single-word-spelling skills (which often account for the success of students with NLD in the primary school years)

●Weakness in visual-spatial organization

●Difficulty in social reasoning

●Weakness in higher-order reading comprehension and written expression (usually not manifest until grade 3 or in higher grades)

●Weaknesses in attention and executive function

●Math disability (usually after grade 3)

●Anxiety

●Depression

(See "Autism spectrum disorder in children and adolescents: Clinical features", section on 'Associated conditions'.)

Factors affecting clinical expression — Personal (intrinsic) and environmental factors affect the clinical expression of LD, which varies from one student to the next.

Individual factors — The clinical expression of LD is not simply a reflection of impairment in a given skill but results from the interaction of many factors, including co-occurrence with psychiatric conditions or internalizing and externalizing symptoms [55,56]. (See 'Comorbidities' below.)

Environmental factors: School — The environment has an important impact on the clinical expression of LD. Classrooms that are organized and instruction that is systematic and predictable can help to mitigate the degree to which intrinsic learning weaknesses affect the child's learning.

Teachers who are skilled at determining a student's capacity to understand, remember, and follow oral instructions and who can adjust the language load by simplifying instructions, providing repetition, and/or providing visual supports can reduce the impact of language delays on the child's learning and thereby improve the child's overall performance when they are expected to learn to read or count. (See "Specific learning disorders in children: Educational management", section on 'Quality instruction'.)

Teachers who understand the impact of executive dysfunctions, which occur in children with ADHD and other disorders, can mitigate the impact of executive dysfunctions by providing extra monitoring, supervision, and organizational supports. All of these classroom strategies help to reduce the effort that the student has to make when addressing learning tasks related to their areas of weakness, regardless of LD type. However, the consistency with which such teaching strategies are practiced is highly variable. (See "Attention deficit hyperactivity disorder in children and adolescents: Overview of treatment and prognosis", section on 'School-based interventions' and "Attention deficit hyperactivity disorder in children and adolescents: Overview of treatment and prognosis", section on 'Psychosocial interventions'.)

Environmental factors: Home — Similarly, the home environment can affect the expression of learning problems. Home environments in which reading is practiced, or that provide structure (eg, rules and directions), predictability, and routine, can moderate the effects of language weaknesses and/or executive dysfunctions. These factors are not always considered to be a specific focus of educational intervention, but when they are implemented successfully, they help prepare the student to learn in the classroom. Language and executive dysfunction are particularly important areas to target for any student with an LD, regardless of the LD type [30,57,58].

Clinical presentation — Pediatric health care providers should consider the possibility of LD in children who have risk factors and children who have problems at school (whether the problems are related to academic achievement, behavior, attention, or social interaction). LDs interfere with all aspects of life, not just academics [59]. Deficits in one area usually lead to, or are associated with, difficulties in another [30]. (See 'Risk factors' above.)

Problems at school may be related to:

●Academic difficulty – Poor performance in one or more academic areas.

●Negative self-concept – Poor performance at school can result in a negative self-concept and reluctance to participate in learning, even for those areas that may be personal strengths for the child.

●Behavior problems – Children with LD may show overt hostility or resistance to caregiver or teacher demands or get discouraged quickly [60-65].

●Social interaction – Children with LD may have difficulty making friends because they fail to remember the names of peers, have difficulty using language to participate in conversations, have coordination problems that interfere with playing games, or have language/cognitive problems that prevent them from understanding games with complex rules [61,62]. Children with LD also may fail to fully understand social nuances or may not understand the social intentions of others. All of these factors can interfere with their social success.

Clinical course — Limited information is available about the persistence of LDs over time. For example, reading disability is estimated to have a diagnostic stability rate of 28 to 78 percent, depending upon the study [66,67]. These estimates are too wide to be clinically meaningful and are explained, in part, by the varying criteria used to define reading disability, the age at which the original diagnosis was made, and by treatment effects.

Diagnostic stability for reading disability is lower among younger children (eg, kindergarten and grade 1 students), suggesting that reading difficulty in younger children may have a variety of causes, some of which are more amenable to treatment than others. Among older children (eg, grade 3 and higher grades), reading disability tends to persist over time. Even though reading skills may improve, reading decoding and (more commonly) reading fluency skills continue to measure below normal. Variation in the clinical expression of reading disability over time makes consistent measurement and identification more problematic [68-70]. (See "Reading difficulty in children: Clinical features and evaluation", section on 'Clinical course'.)

Less information is available about the diagnostic stability of other types of LD. In one study, 65 to 70 percent of children who had difficulty with math throughout kindergarten had persistent math difficulty in grade 5 [71].

Comorbidities — LD usually do not exist in isolation. They co-occur with other LDs, with internalizing and externalizing symptoms, and with many neurodevelopmental disorders [55,56]. For this reason, the evaluation of LD must be broad and should include an evaluation for a range of coexistent conditions.

In a sample of 485 clinically referred children referred for evaluation, 65 percent had LD; writing disability was most common (92 percent) [15]. Among children with writing disability, 15 percent had coexisting reading and math disability; 14 percent had coexisting reading disability; and 13 had coexisting math disability. In a separate study of 949 children with neurodevelopmental conditions, LD co-occurred in 71 percent of children with ADHD, 67 percent of children with autism, 79 percent of children with bipolar disorder, and 18 to 19 percent of children with oppositional defiant disorder, adjustment disorder, anxiety, and depression [56]. These findings underscore the importance of a comprehensive assessment for a variety of LD syndromes and psychiatric conditions in all children with LD.

The lack of consistent LD case identification makes it difficult to accurately determine the frequency of co-occurrence of LD with psychiatric conditions. However, the general trend for overlap is striking, with most studies suggesting LD in 20 to 70 percent of children with behavioral or psychiatric conditions (eg, ADHD, anxiety, depression) [41,56,72,73]. This is a much higher incidence than would be expected for the population as a whole.

DIFFERENTIAL DIAGNOSIS — The differential diagnosis of learning disorders (LD) includes [1,23,74]:

●Mild intellectual disability (see "Intellectual disability (ID) in children: Clinical features, evaluation, and diagnosis")

●Below-average intelligence (ie, intelligence quotient [IQ] scores between 70 and 89)

●Hearing or vision impairment

●Psychiatric conditions, such as attention deficit hyperactivity disorder or emotional disturbance (eg, depression or anxiety) (see "Pediatric unipolar depression: Epidemiology, clinical features, assessment, and diagnosis" and "Attention deficit hyperactivity disorder in children and adolescents: Clinical features and diagnosis", section on 'Core symptoms' and "Attention deficit hyperactivity disorder in children and adolescents: Clinical features and diagnosis", section on 'Clinical features')

●Caregiver/school expectations that are discordant with the student's abilities and interests

●Environmental factors (eg, lack of opportunity, frequent school absences, poor teaching, and cultural factors, such as English as a second language)

●Sleep problems (see "Cognitive and behavioral consequences of sleep disorders in children")

Other causes for learning failure include neurologic conditions (seizures, static or progressive neurologic disorders), genetic causes medication side effects, or substance abuse, among others. These conditions can be identified by history, examination, and ancillary evaluation (eg, audiology, vision screening). Other conditions may require more specialized testing and/or referral. Qualitative observations and/or the student's report card often can identify LD, but psychometric testing is used to make a formal diagnosis. The presence of LD along with the conditions listed above is common.

The comprehensive evaluation for a child with learning difficulty is discussed separately. (See "Specific learning disorders in children: Evaluation", section on 'Comprehensive evaluation'.)

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Here are the patient education articles that are relevant to this topic. We encourage you to print or email these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient education" and the keyword[s] of interest.)

●Basics topic (see "Patient education: Learning disabilities (The Basics)")

SUMMARY

●Terminology – The core feature of specific learning disorders (LDs) is an intrinsic cognitive difficulty that results in academic achievement at a level less than expected for the individual's age (table 1). (See 'Terminology' above.)

●Risk factors – Risk factors for LD include family history of LD, poverty, prematurity, developmental and mental health conditions (eg, attention deficit hyperactivity disorder [ADHD], depression), prenatal alcohol exposure, neurologic conditions (eg, seizure disorder, neurofibromatosis), chromosomal disorders (eg, fragile X syndrome, Turner syndrome), certain chronic medical conditions (eg, type 1 diabetes mellitus), and history of central nervous system infection or irradiation. (See 'Risk factors' above.)

●Etiology and pathogenesis – LDs are caused by inborn or acquired abnormalities in brain structure and function and have a multifactorial etiology. They are not caused by eye problems. (See 'Etiology and pathogenesis' above.)

●LD syndromes – LDs are a heterogeneous group of disorders. However, patterns of learning problems often cluster, resulting in commonly recognized LD syndromes, including (table 2):

•Reading disability (dyslexia) (see 'Reading disability' above)

•Disorders of written expression (dysgraphia) (see 'Writing disability' above)

•Mathematical disorders (dyscalculia) (see 'Math learning disorder' above)

•Nonverbal LD (nonlanguage-based LD, right hemisphere dysfunction) (see 'Nonverbal learning disorder' above)

•Language-based LD (see 'Language-based learning disorder' above)

●Factors affecting clinical expression – The clinical expression of LD is influenced by concomitant internalizing and externalizing symptoms and psychiatric conditions, the classroom environment (eg, amount of structure, skill of teacher), and the home environment (eg, amount of structure [eg, rules, directions], predictability, routine). (See 'Factors affecting clinical expression' above.)

●Clinical presentation – Pediatric health care providers should consider the possibility of LD in children who have risk factors and children who have problems at school (whether the problems are related to academic achievement, behavior, attention, or social interaction). (See 'Clinical presentation' above.)

●Comorbidities – LD frequently occur with other neurodevelopmental disorders (eg, behavior disorders, ADHD, autism). (See 'Comorbidities' above.)