Version May 2024
INTRODUCTION — People with developmental and intellectual disabilities (ID) are living longer than in the past and most are living in the community rather than in institutional settings. Thus, the primary care clinician will provide health care for increasing numbers of adult patients with ID and cognitive impairment. This topic will address the primary care management of these individuals.
The diagnosis, evaluation, and management of children with ID are presented separately:
●(See "Intellectual disability (ID) in children: Clinical features, evaluation, and diagnosis".)
●(See "Intellectual disability in children: Evaluation for a cause".)
●(See "Intellectual disability (ID) in children: Management, outcomes, and prevention".)
DIAGNOSIS AND CLASSIFICATION — Developmental disabilities refer to a number of different conditions with onset in childhood; intellectual disability (ID) is a nonspecific term that refers to a mental capacity below normal due to any condition that impairs development of the brain before birth, during birth, or in the childhood years. ID is sometimes referred to as cognitive impairment or cognitive adaptive disability.
Individuals with ID are often characterized by their intelligence quotient (IQ). The IQ, a term first coined in the 1900s, is assessed by a variety of standardized tests including the Simon-Binet scale or the Wechsler Adult Intelligence Scale. The normal range for IQ falls between 90 and 110. An IQ two standard deviations below the mean (ie, IQ <70) is consistent with ID. ID is further classified as mild (IQ 50 to 69); moderate (IQ 35 to 49); severe (IQ 20 to 34); or profound (IQ <20).
The diagnosis of ID involves an assessment of the individual's cognitive and functional abilities that goes beyond simply determining the IQ. The American Association of Intellectual and Developmental Disabilities (AAIDD) advocates a three-step evaluation process [1]:
●Measure the IQ
●Assess behavior and emotional skills
●Assess the impact of the individual's limitations on their ability to manage activities of daily living (ADLs)
The Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) diagnostic criteria for ID are consistent with this assessment and require documentation of deficits in intellectual and adaptive functioning with onset during the developmental period [2]. (See "Intellectual disability (ID) in children: Clinical features, evaluation, and diagnosis".)
Frequently, individuals with ID can function well in early childhood, with limitations not becoming apparent until they are challenged with learning upon entering school.
Many adults with mild ID can live independently in the community. However, those with IQs below 50, accounting for approximately 10 percent of those with ID, will require significant support to perform ADLs (table 1).
EPIDEMIOLOGY — Intellectual Disability (ID) affects approximately 1 percent of all people globally [3]; the degree of disability within this group is quite variable, since the intelligence quotient (IQ) is just one component for determining ID. In 2016, the prevalence of ID among United States children aged 3 to 17 years was 1.14 percent [4], with significant variation between states. (See "Intellectual disability (ID) in children: Clinical features, evaluation, and diagnosis".)
Patients with ID have shortened life expectancy (ranging from 13 to 20 years shorter), increased numbers of medical problems, and decreased rates of recommended preventive health interventions compared with the general population. These issues can be attributed to multiple factors [5,6]:
●Genetic factors that result in a greater burden of somatic health problems, in addition to their ID
●Communication difficulties involving the patient, caregivers, and health providers
●Deficiencies in the structure and funding of health services for this population
These issues often result in disparities between health services provided to those with ID compared with the general population [7]; patients with ID are less likely to receive adequate medical care despite their increased burden of chronic health problems [6].
ETIOLOGIES — Conditions that impair intellectual development may be related to a genetic abnormality or caused by a brain injury occurring prenatally, perinatally, or in early childhood. Injuries resulting in impaired brain development may be related to trauma, metabolic abnormalities (eg, hypothyroidism), toxin exposure (eg, alcohol), or infections (eg, meningitis or encephalitis). Fetal alcohol syndrome (FAS) is an important cause of intellectual disability (ID). However, in many cases, no definitive cause can be determined. (See "Intellectual disability (ID) in children: Clinical features, evaluation, and diagnosis" and "Intellectual disability in children: Evaluation for a cause".)
Rates of brain injury in childhood have declined due to several initiatives: prevention of traumatic brain injuries (eg, use of car seats and bicycle helmets), prenatal maternal immunization for rubella, Haemophilus influenzae type b (Hib) immunization in infancy to protect against Hib meningitis, and newborn blood screening to detect disorders such as hypothyroidism and phenylketonuria (PKU).
Genetic disorders most common cause of severe ID — Genetic disorders are responsible for the majority of those with severe ID (intelligence quotient [IQ] <50), while mild ID is more likely to be associated with nongenetic factors [8]. While, over 500 different genetic defects have been associated with ID [8], the two most common genetic etiologies of ID are Down syndrome and Fragile X Syndrome.
Down syndrome, the most common genetic cause of ID, is caused by a sporadic chromosomal disorder resulting in a third chromosome at the 21st position (Trisomy 21). (See "Down syndrome: Clinical features and diagnosis".)
Fragile X syndrome is caused by a single gene defect on the X chromosome. X-linked disorders primarily affect males, with females being carriers and transmission of the defect through the maternal line. Other examples of X-linked inheritance associated with ID include Hunter syndrome, Lesch Nyhan syndrome, and Duchenne muscular dystrophy. (See "Fragile X syndrome: Clinical features and diagnosis in children and adolescents" and "Mucopolysaccharidoses: Clinical features and diagnosis" and "Hyperkinetic movement disorders in children", section on 'Lesch-Nyhan syndrome' and "Duchenne and Becker muscular dystrophy: Clinical features and diagnosis", section on 'Cognitive and behavioral disorders'.)
Many genetic defects do not directly cause mentation difficulties but lead to metabolic disorders that result in developmental impairment. Hundreds of inborn errors of metabolism have been identified, affecting 50.9 per 100,000 live births globally [9]. Phenylketonuria (PKU) is an example of a single gene disorder; the abnormal gene causes production of a defective form of the enzyme phenylalanine hydroxylase. This enzyme is responsible for the conversion of the amino acid phenylalanine to tyrosine. The resulting buildup of phenylalanine causes developmental disability. However, if such individuals are placed on a phenylalanine-free diet, they can lead relatively normal lives [10]. (See "Overview of phenylketonuria".)
Early identification of genetic metabolic disorders through state newborn screening programs has led to improved survival and health status of individuals diagnosed with these conditions. Newborn screening programs in the United States vary by state but always include PKU and congenital hypothyroidism (table 2) [11]. (See "Overview of newborn screening".)
APPROACH TO THE PATIENT WITH ID
Challenges and barriers to care — There are multiple challenges to providing primary care for adult patients with intellectual disability (ID). Patients may not be able to adequately communicate their needs or concerns; caregivers who accompany them to appointments may be unable to provide essential information; frequent relocations between group homes impedes the development of a trusting patient/provider relationship; and patients may be fearful about components of the physical examination or diagnostic testing. Combining these barriers to care with the increased number of health issues among the intellectually disabled, along with the extra clinical time needed to provide even routine care, can compromise the ability to provide thorough, quality care. Nonetheless, these patients deserve the same intensity of preventive health services and comprehensive care as all others.
When providing care to those with ID:
●Evaluate and consider the nature of the living situation:
•Individuals with ID can live in a variety of community settings, dependent upon their ability to care for themselves. Many live with their parents throughout their life, although disruptions in care may occur as parents age or die.
•Non-family settings range from independent living (alone or in shared-living situations with friends) to more structured residences such as supervised group homes, assisted-living, or traditional skilled-nursing facilities. Individuals living in licensed non-family settings may have facility-related access to health care. Changes in residential settings due to insurance, age, or jurisdictional reasons may lead to fragmentation of health care.
●Do not make assumptions about the degree of communication skills that an individual with ID possesses. Even when communication skills are limited, the patient should be addressed directly and always treated in a respectful and caring manner. Acknowledge the patient's right to consent to examinations or tests, even if verbal communication is limited.
●Individuals who are nonverbal or have limited verbal communication skills are at greater risk for poor nutrition, overmedication, injury, and abuse. Abuse may be either physical or sexual and may involve other patients or facility staff.
●For patients with limited communication abilities, the medical history will often be provided by the caregiver accompanying the patient. Physical complaints may be vague and the history limited. Taking the time to contact the caregiver who is closest to the patient is helpful in understanding what prompted the visit. Two-way written communication between health care provider and that caregiver is also essential.
●It is best to approach fearful individuals slowly, after a period of conversation, and perform a limited examination until they have become comfortable with the provider. For some patients, the clinician's white coat can be frightening, while others may find it a reassuring sign that it is safe to be touched by this individual.
●In very difficult situations, pre-sedation with an anxiolytic (eg, lorazepam) may be required to obtain testing, such as an electrocardiogram, or to perform a pelvic examination. Home visits can provide the opportunity to pursue an examination in a more comfortable and safe environment for the patient.
Routine health care — General screening and immunization guidelines for routine health maintenance should be followed for individuals with ID. Routine preventive services should include periodic dental examination, age-appropriate cancer screening, and immunizations. (See "Overview of preventive care in adults".)
In addition to care routinely provided to the general population, particular interventions should be considered for patients with ID. For example, the Massachusetts Department of Developmental Services has published guidelines specific to these patients [12].
Suggestions for routine health care in this population include:
●Evaluate for early stages of mental illness, which is more common in this population [13]. Obsessive-compulsive disorder, anxiety, and depression are common, and early intervention may prevent more serious impairments and secondary disability. While changes in behaviors, social interactions, and sleep patterns can be from underlying medical conditions, behavioral support plans should also be considered. (See 'Behavioral disorders' below and 'Mental illness' below.)
●Screening laboratory studies (blood chemistries, complete blood count, thyroid-stimulating hormone) should be obtained at regular health maintenance visits to supplement the limited available information for patients with impaired communication [12]. Decisions to order laboratory studies should be balanced against the difficulty of obtaining a blood specimen, and the lower predictive value of positive test results in an asymptomatic population.
●People in institutional care should be periodically evaluated for evidence of infectious diseases such as tuberculosis and hepatitis C. Patients who do not have documentation of hepatitis B vaccination should be tested for hepatitis B and vaccinated if negative. (See "Hepatitis B virus immunization in adults", section on 'Indications'.)
ACIP recommends hepatitis A vaccination for adults at risk for hepatitis A virus (HAV) infection, including those living in group homes and those attending nonresidential day care facilities, as well as those at risk for severe disease from HAV infection, and for any adult requesting vaccination [14]. (See "Hepatitis A virus infection: Treatment and prevention", section on 'Indications'.)
Patients should be offered appropriate testing for sexually transmitted diseases, including HIV testing; legal guardians may need to be contacted for their decision and consent regarding HIV testing. (See "Screening and diagnostic testing for HIV infection", section on 'Routine screening'.)
Although following routine health maintenance guidelines is the goal, a commonsense approach should be taken. As an example, in the case of a fearful, uncooperative, combative patient, where anesthesia is required in order to perform an adequate pelvic examination for cervical cancer screening, the risks of anesthesia need to be weighed against the risk of cervical cancer in that individual.
Scheduling visits — While the periodic health examination in the general population may not be the most efficient way to provide primary care, and many advocate providing preventive health services in the context of sick visits, scheduled routine visits may have greater impact and be more important for patients with ID. A system of providing medical visits only on demand is less effective for a population with limited ability to communicate who may not be able to express need. Additionally, these patients often require extra time for a visit because of the complexity of the patient/caregiver/clinician interaction and multiple underlying social, behavioral, and emotional difficulties.
In a study in the United Kingdom, for example, in which structured health checks were provided by 40 general practices for 180 patients with ID, 51 percent had new health problems identified; serious treatable health problems, including breast cancer, dementia, diabetes, and hypothyroidism were identified in 16 patients [5].
Issues of special concern
Legal issues — Issues of guardianship and who can consent for the patient should be clarified early on in the medical relationship. Many individuals with ID do not require a legal guardian if they have the capacity to receive and evaluate information and make and communicate decisions required to maintain their health and safety. However, there is often a need to establish a legal or medical guardianship. The guardian may be a relative, a designated representative, or a social service agency or worker. For those individuals who remain under the care of their parents, a successor guardian for an aging parent should be identified and paperwork signed to legalize the decision.
If there is ever a controversy over medical care, the health care provider can play an important role as the patient's advocate.
End-of-life issues should be discussed prior to the development of a life-threatening event. The patient's wishes, as well as the family's concerns and preferences, are important to solicit. ID itself is not a reason for routine do-not-resuscitate (DNR) status; such decisions should include the nature of the individual's terminal illness, likelihood of resuscitation success, and the patient's and family's religious and cultural beliefs.
Sexuality — Sexuality is an area often overlooked, as it is often assumed that individuals with ID are not sexually active. Issues related to birth control and the possibility of sexually transmitted diseases should be considered and addressed with the patient, family, and caregivers. Additionally, many individuals are living independently in the community and counseling regarding sexual abuse, alcohol, and substance abuse is important.
Increased risk of abuse — Individuals with ID are at increased risk of experiencing interpersonal violence, including physical, sexual, and caregiver violence. In a systematic review and meta-analysis of three studies, there was a 60 percent increased risk for experiencing violence among persons with ID compared with the general population (odds ratio [OR] 1.60, 95% CI 1.05-2.45) [15]. Another two studies cited in the systematic review but not included in the meta-analysis found that individuals with intellectual impairment had the highest rates of violence compared with individuals with other types of disability, including mental illness and physical or sensory impairments.
COMMON PROBLEMS — People with intellectual disability (ID) are at risk for a variety of social problems, and many also suffer from underlying congenital or metabolic abnormalities which may cause unique medical and physical problems. Common comorbid conditions include seizure disorders, cerebral palsy (CP), gastrointestinal motility problems, thyroid disease, and behavioral disorders. Appropriate screening should be performed for cardiovascular risk. Unfortunately, this population is also participating in the obesity epidemic, with its resulting increase in diabetes. A table highlights conditions that are commonly missed in this population (table 3).
Mental illness — The diagnosis and treatment of mental illnesses and other serious disorders in this population are often delayed, inadequate, or not provided at all. Additionally, evidence is quite limited regarding the effectiveness of mental health interventions in persons with ID [16]. While behavioral issues are often the presenting complaint when patients with ID are brought in for psychologic evaluation, depression, anxiety and other mental health disorders often play a role. Psychiatric comorbidities are common, affecting 31 percent of subjects with ID (mean age 22.6 years) who were followed over a course of 14 years [17]. In this Australian cohort, only 10 percent of those with psychopathology had received mental health intervention during the 14-year study period.
Seizure disorder — Seizure disorders are more prevalent in patients with ID than the general population. The incidence of seizures is highest in those with the lowest intelligence quotient (IQ) and affect upwards of 50 percent of patients with ID and concurrent CP [18]. A comorbid seizure disorder is associated with a death rate three times higher than for those without epilepsy [19]. It is important to discuss seizure safety with those that care for the patient.
It is not unusual for more than one anticonvulsive agent to be required to control seizures in a patient with severe ID. Periodic measurement of serum levels for anticonvulsants will help maintain therapeutic ranges, avoid breakthrough seizures, and decrease medication toxicity. A trial taper of anticonvulsants if the patient has not had a seizure in two years has been advocated by some [20], although ID is a risk factor for seizure recurrence off medication. (See "Overview of the management of epilepsy in adults".)
Cerebral palsy — Cerebral palsy (CP) refers to the presence of a nonprogressive motor impairment and, like ID, is a nonspecific term. While not all individuals with CP suffer from ID, up to one-third of all intellectually disabled individuals are affected by CP [21]. CP presents a variety of challenges to the patient and their caregivers, including spasticity and immobility, high rates of strabismus and cerebral visual impairment, bowel and bladder dysfunction, and altered growth and nutrition. (See "Cerebral palsy: Classification and clinical features".)
Pharmacologic treatment for spasticity includes the use of various medications such as oral benzodiazepines, dantrolene, baclofen, and tizanidine; injectable botulinum toxins, phenol, and alcohol; and intrathecal baclofen. Oral medications and intrathecal baclofen are used to address generalized spasticity, while injectable agents are used to treat localized spasticity [22]. Orthopedic surgeries may also be necessary. (See "Cerebral palsy: Overview of management and prognosis".)
Careful skin hygiene is important for patients with CP or other significant movement limitations to prevent problems with pressure ulcers. Bone demineralization with consequent fractures, and decubitus ulcers, may occur secondary to longstanding immobility and nutritional deficiencies. A good relationship with a rehabilitation center can be important for assuring the proper fitting of wheelchairs and other supportive devices.
Dysphagia — Upper gastrointestinal dysmotility can cause dysphagia, esophageal reflux, and gastric emptying disorders. This may lead to dental erosion, esophagitis, anemia, feeding problems, aspiration, and pneumonia.
Dysphagia can be seen in up to 5 percent of patients with ID, which is slightly higher than the prevalence the general population (approximately 4 percent) [23]. The use of a modified barium swallow and a speech and swallowing evaluation can be helpful to determine the degree of swallowing dysfunction and guide the use of specialized diets. (See "Oropharyngeal dysphagia: Clinical features, diagnosis, and management".)
Consultation with a speech or language pathologist can provide insight into feeding strategies and eating behaviors. Methods to minimize aspiration risk include modifying the consistency of foods to include pureed foods and compounds to thicken liquids to a honey-like consistency. Other important steps include feeding meals in a quiet, non-stressful setting and feeding slowly in an upright position.
The use of gastrostomy tubes (G-tubes) or jejunostomy tubes (J-tubes) to decrease aspiration risk and provide adequate nutrition for those who are incapable of taking in enough calories to maintain weight may be considered. The use of such feeding tubes to prevent aspiration pneumonia is controversial [24]. G-tube feeds can be given slowly while the individual sleeps to avoid the use of this disruptive technology during the day. It is important to instruct caregivers to keep the head of the bed elevated at a 30 degree angle to avoid reflux of stomach contents. J-tubes may be a better choice than G-tubes. (See "Enteral feeding: Gastric versus post-pyloric".)
Constipation — Constipation has been reported in up to 40 percent of individuals with ID, usually secondary to immobility and lack of exercise. However, specific gastrointestinal dysfunction may play a role and medical conditions such as hypothyroidism should be considered. Psychotropic and other medications with anticholinergic effects are often contributing factors. Inadequately treated constipation may cause fecal impaction, intestinal obstruction, and even death. Since the history of bowel function may be difficult to obtain, constipation may be missed as a cause of patient distress [25]. Plain films of the abdomen, with a specific request for the radiologist to assess stool content, may detect significant stool retention in the colon and can be helpful when the history is not reliable.
Strategies for dealing with this common condition include increasing fluids and the use of laxatives. Daily laxatives such as polyethylene glycol or senna may be required; tolerance to stimulant laxatives is uncommon [26]. For more significant constipation, stimulant suppositories or enemas given every three to four days may be necessary. (See "Management of chronic constipation in adults".)
Behavioral disorders — Behavioral disorders are frequent among people with ID and range from self-injurious actions to other aggressive activities which may be directed at other individuals and caregivers. The most common forms of these behaviors include head-banging, hand-biting, and excessive self-rubbing and scratching. Behavioral disruptions may be a normal reaction to minor changes in the patient's surroundings, appropriate for the developmental age of the patient. Patience and redirecting behavioral treatments should be tried before starting psychotropic medications.
Communication difficulties can significantly impede the evaluation of behavioral disorders. Any change in baseline behavior should prompt an investigation for an underlying source of pain, or other contributing medical factor. For example, a report of secondary medical causes of behavioral change ranked constipation as the number one problem [27], and others have noted an association with menstrual discomfort [28]. Potential for unreported traumatic injuries should be considered.
Potential causes for specific behavioral abnormalities should be evaluated, including a careful physical examination to look for sources of discomfort related to such irritations as infections (dental caries, respiratory, skin, urinary tract), pain from minor annoyances such as cerumen impaction, or more serious conditions such as celiac, gastroesophageal reflux disease (GERD), fractures, or testicular torsion.
A multidisciplinary approach is helpful in treating behavioral disorders. Behavioral modification therapies should be attempted, before medications are initiated. Behavioral techniques include providing alternative options for the individual to choose and providing follow through with appropriate rewards or consequences.
Though antipsychotics are commonly used to treat aggressive behavior for nonpsychotic individuals with ID, the use of antipsychotics for behavioral control should be reserved for resistant behaviors that result in significant self-injury or potential harm to others [29]. Medications should be weaned to the lowest effective doses once behaviors are stabilized [30]. Newer atypical antipsychotic agents minimize the risk of extrapyramidal side effects but still carry an increased risk for inducing the metabolic syndrome, weight gain, and diabetes. Patients who are treated with psychotropic medications need frequent monitoring for potential side effects (table 4). (See "First-generation antipsychotic medications: Pharmacology, administration, and comparative side effects" and "Second-generation antipsychotic medications: Pharmacology, administration, and side effects".)
Rates of antipsychotic use are reported in up to 45 percent of individuals in institutions and 20 percent in the community [31]. A systemic review looking at the use of antipsychotics (risperidone, quetiapine) for patients with ID and aggressive behavior found only limited evidence of efficacy of risperidone in reducing aggression and conduct problems in children aged 5 to 18 with disruptive behaviors and no evidence to support the use of quetiapine for such disorders [31].
In addition, attention-deficit hyperactivity disorder (ADHD) is more prevalent in people with ID, compared with the general population. There is no evidence from randomized trials that risperidone is effective for management of ADHD in patients with ID [32], although it has been prescribed for this indication.
Dementia and cognitive decline — Adults with ID are presenting with late-life cognitive decline with increasing frequency; in this population, there are distinct challenges for evaluation, diagnosis, and management. In particular, this is an issue for patients with Down syndrome who have a significantly increased risk for Alzheimer disease. (See 'Down syndrome' below and "Down syndrome: Clinical features and diagnosis", section on 'Dementia/Alzheimer disease'.)
There are no generally accepted criteria for memory or cognitive assessment in adults with ID. A diagnosis of dementia requires evidence of a change of function from a previous baseline; a family member or caregiver is an essential provider of this information. Asking specific questions about a change in participation in hobbies or activities, as well as documenting any changes in functional activities of daily living (ADLs), can be useful ways to elicit such information. While cognitive screening tools, such as the Mini-Mental State Examination have not been validated for diagnosing dementia in this population, administering an evaluation instrument, such as the modified CAMDEX informant interview [33] and/or the IBR Mental Status Examination, may be helpful in establishing a baseline for follow-up examinations and providing some objective information [34-36]. It is also important to exclude possible treatable contributors to cognitive decline including adverse effects of medications, sleep problems, psychosocial and environmental stressors, and metabolic abnormalities. (See "Evaluation of cognitive impairment and dementia", section on 'Evaluation'.)
Treatment involves both pharmacologic and nonpharmacologic approaches. These are discussed in detail separately. (See "Treatment of Alzheimer disease" and "Management of neuropsychiatric symptoms of dementia" and "Management of the patient with dementia".)
Oral hygiene — Oral hygiene is often overlooked [37]. Periodontal disease is common. Mild sedation may be needed for outpatient dental visits; deeper sedation requiring monitoring is occasionally indicated for patients intolerant of outpatient care.
SYNDROME SPECIFIC ISSUES — When caring for an individual with an intellectual disability (ID), a search for the underlying cause is helpful; however, in many instances the cause of the individual's disability is not discernible. Genetic testing can be helpful and may be useful for advising families to the possibilities of an inherited disorder.
Various conditions are associated with specific medical risks that may require special screening. The three major congenital etiologies of ID are Down syndrome, fragile X syndrome, and fetal alcohol syndrome (FAS).
Down syndrome — Down syndrome, resulting from an extra chromosome at the 21st position, is seen with increasing frequency with advancing maternal age [38]. The clinical features, diagnosis, and management of children with Down syndrome are discussed elsewhere. (See "Down syndrome: Clinical features and diagnosis" and "Down syndrome: Management".)
The median age of death for patients with Down syndrome has increased from 25 to 60 years of age [39]. The primary care of adult patients with Down syndrome is like the general adult population, with additional screening for conditions specific to these patients. The Global Down Syndrome Foundation Medical Care Guidelines for Adults with Down Syndrome Workgroup has published recommendations regarding screening for this patient population [40].
Down syndrome is associated with cardiac abnormalities, particularly septal defects such as endocardial cushion defects and tetralogy of Fallot. Children with Down syndrome are routinely evaluated for the presence of cardiac abnormalities in infancy and childhood. If adult patients did not have an echocardiogram in childhood or the results are not available, an echocardiogram should be obtained to rule out structural heart disease. Patients with a normal echocardiogram do not need a repeat in adulthood unless there are new physical examination findings, a change in cardiac function, or symptoms that suggest cardiac dysfunction [41]. (See "Down syndrome: Management", section on 'Cardiac disease'.)
Thyroid dysfunction is common in patients with Down syndrome. Individuals with Down syndrome have a 30 percent lifetime risk of developing hypothyroidism; adults should be screened every one to two years with a thyroid-stimulating hormone [40].
Obstructive sleep apnea is also common in these patients and may be diagnosed in childhood. There are no screening recommendations for obstructive sleep apnea in adults with Down syndrome, although the diagnosis should be considered for patients with new or worsening cognitive or behavioral issues, cardiovascular disease, and obesity [40]. (See "Down syndrome: Management", section on 'Sleep apnea'.)
Visual impairments, including amblyopia, refractive errors, cataracts, and glaucoma, are common. Hearing impairment is also common. Annual ophthalmologic and auditory examinations are recommended and should be reassessed in the evaluation of a new or worsening behavioral problem.
Patients with Down syndrome have a decrease in cell-mediated immunity. Reduction in cell-mediated immunity results in a slightly higher rate of leukemia than in the general population, which is typically manifested in childhood. Additionally, these individuals are at increased risk for infection.
Ligamentous laxity is associated with Down syndrome and may cause problems if there is atlantoaxial instability (AAI) with increased mobility at C1-2. This is seen in about 7 percent of Down syndrome patients. The majority of those with AAI remain asymptomatic, and screening cervical spine radiographs in those without myelopathic symptoms are not indicated [40]. However, symptoms due to spinal cord compression may develop, and annual screening for cervical myelopathy should be done with a targeted history and physical examination, looking for neck or shoulder pain, gait change, or new incontinence. Traditionally, if an individual plans to engage in contact sports or participate in athletic activities such as the Special Olympics, pre-participation cervical radiographs are obtained; however, there are no studies demonstrating that avoidance of physical activity in an asymptomatic individual with AAI prevents spinal cord injury [40]. Preoperative neck radiographs (lateral cervical spine films: neutral, flexed, and extended views) should be obtained if intubation for general anesthesia is planned. (See "Down syndrome: Management", section on 'Atlantoaxial instability'.)
Patients with Down syndrome have a significantly increased risk for Alzheimer dementia, which should be considered in the individual ≥40 years whose function begins to deteriorate. Beginning at age 40 years, we assess patients annually by evaluating changes in baseline functioning through interview of the patient and their caregivers [34,40]. Alzheimer dementia occurs at a younger age in people with Down syndrome than the general population, although it is unusual before the age of 40. Approximately 20 percent of patients with Down syndrome over the age of 45 have dementia [42], which is correlated with increased mortality risk in these individuals [43]. (See "Down syndrome: Clinical features and diagnosis", section on 'Dementia/Alzheimer disease'.)
Alzheimer dementia is associated with neurofibrillary tangles and beta-amyloid plaques. The gene for beta-amyloid precursor protein (APP) is located on chromosome 21. It is thought that over-expression of this gene, due to the extra chromosome, results in excess APP production. Additionally, chromosome 21 codes for superoxide dismutase (SOD-1); increased activity of this enzyme may enhance the production of hydroxyl radicals and further contribute to neural damage [44]. (See "Genetics of Alzheimer disease", section on 'Trisomy 21'.)
In general, patients with Down syndrome and Alzheimer disease should be managed similarly to other patients with dementia, although treatment trials in this population are limited. (See "Treatment of Alzheimer disease".)
Fragile X syndrome — Fragile X syndrome is the most common form of inherited ID in males. A defect of the FMR1 (fragile X messenger ribonucleoprotein 1) gene on the X chromosome leads to problems with the production of the FMRP protein, assumed to be essential for normal brain functioning. Females, with two X chromosomes, are carriers, though may have some minor symptoms. This syndrome is seen in 1 of every 2000 male births. (See "Fragile X syndrome: Clinical features and diagnosis in children and adolescents", section on 'Diagnosis'.)
Characteristic features include macrocephaly, large ears, strabismus, high palate, and hyperextensible fingers. Speech delays and behavioral problems, including attention deficit, are common with autistic-type behaviors seen in about a quarter of affected individuals. Physical symptoms, such as large testes, are more apparent after puberty. Hand biting or flapping and speech disturbances are also common. Cardiac valve defects may be present, particularly mitral valve prolapse.(See "Fragile X syndrome: Clinical features and diagnosis in children and adolescents", section on 'Clinical features'.)
Diagnosis is established by molecular testing for the FMR1 gene rather than routine chromosome analysis. No specific treatment other than genetic counseling is currently available.
Fetal alcohol syndrome — FAS is the leading cause of preventable ID. While not a genetic condition, FAS is a common disorder, seen in about 1 to 3 per 1000 births in the United States; incidence is likely higher in countries with higher rates of alcohol abuse. Ethanol acts as a toxin on newly forming embryonic cells, particularly during the first trimester when a woman may not yet realize she is pregnant. FAS is the extreme expression of prenatal alcohol consumption causing the abnormalities seen in fetal alcohol spectrum disorders (FASDs). (See "Fetal alcohol spectrum disorder: Clinical features and diagnosis".)
Characteristic facial features include a long philtrum, a wide and thin upper lip, wide nasal bridge, and a small, upturned nose. The "Lip-Philtrum Guide" is a useful tool [45] and is available through the University of Washington website. Central nervous system damage can include microcephaly, seizures, learning disabilities, and developmental delay. Growth deficiency, visual problems, hearing loss, heart defects, and genital urinary tract abnormalities are also seen.
Early identification of FAS can lead to intervention programs to prevent secondary complications. These secondary complications include educational difficulties, mental health problems including attention deficit disorder, substance abuse, and trouble with the law. A stable and nurturing home, educational support services, and consistent supportive environment are helpful in preventing these outcomes.
Prader-Willi syndrome — This most common form of obesity caused by a genetic disorder results from an abnormality of the long arm of chromosome 15. The Prader-Willi syndrome is characterized by infantile hypotonia and failure to thrive. Later in life hypogonadism, mental impairment, and short stature are seen and despite early trouble with maintaining weight, such patients experience hyperphagia, with resulting obesity, which may lead to diabetes mellitus or premature congestive heart failure. (See "Prader-Willi syndrome: Management" and "Prader-Willi syndrome: Clinical features and diagnosis", section on 'Genetics and pathogenesis'.)
Strict food supervision, physical activity, and a special education program are the only treatments. Genetic testing is helpful with predicting the risk of recurrence so that appropriate counseling may be given.
SUMMARY AND RECOMMENDATIONS
●Primary care of adults with ID – Adult primary care services are becoming more important for people with intellectual disability (ID), as they are living longer and living in the community. The diagnosis of ID is based on assessment of the intelligence quotient (IQ; <70), an individual's behavioral and emotional skills, and their ability to manage activities of daily living (ADLs). (See 'Introduction' above and 'Diagnosis and classification' above.)
●Etiology of ID in adults – The most common genetic etiologies of ID are Down syndrome and Fragile X Syndrome. Fetal alcohol syndrome (FAS) is the major nongenetic cause of ID. However, a specific etiology cannot be determined for many patients with ID. (See 'Etiologies' above.)
●Approach to caring for adults with ID – In providing care for patients with ID, it is important to understand the living situation, to effectively communicate with people who can provide accurate medical historical information if the patient is unable to do so, to recognize the potential for injury and abuse, and to try to accommodate patient's fears while providing quality health care. Screening for infectious disease in institutionalized patients (tuberculosis, hepatitis B, hepatitis C) and screening laboratory studies to supplement a limited patient history may be indicated. (See 'Approach to the patient with ID' above.)
●Common medical problems – Medical problems common to this population include mental illness and behavioral disorders, seizure disorder, cerebral palsy (CP), dysphagia, and constipation. Constipation may affect up to 40 percent of patients with ID and can be an unsuspected cause of behavioral change. (See 'Common problems' above.)
●Syndrome-specific issues
•Patients with Down syndrome should be evaluated for cardiac abnormalities, visual and hearing impairments, hypothyroidism, and early Alzheimer dementia. An diagnosis of atlantoaxial instability or spinal cord compression should considered if there are symptoms of neck pain or myelopathy. (See 'Down syndrome' above.)
•The Fragile X syndrome is a sex-linked disorder causing macrocephaly and autistic-type behaviors. FAS causes characteristic changes in facial configuration, developmental delay, and often behavioral difficulties. Prader-Willi syndrome can cause obesity. (See 'Fragile X syndrome' above and 'Fetal alcohol syndrome' above and 'Prader-Willi syndrome' above.)
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