Autism Spectrum Disorder

Inattentive
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Diagnosis and reasoning

Delayed speech is a common complaint, often causing significant stress to the affected families. Many such parents seek medical advice for their child after the age of two years. In this case, the parents also complain of behavioral problems and social deficits. This raises concerns regarding autism spectrum disorder (ASD). This child shows many signs typical of ASD. He has impaired social and communication skills in the form of avoidance of eye contact, preferring to play alone, and a joint attention defect (he cannot point to what he wants). Furthermore, he exhibits stereotyped behavior (flapping his hands), hypersensitivity to sensory input (staring at the ceiling lights), resistance to change, and fixated interests (i.e. becomes irritable when his toys are moved). All these signs, along with the delayed development of speech, meet the diagnostic criteria for ASD according to the diagnostic and statistical manual of mental disorders, 5th edition (DSM-5). Since the examination reveals normal motor development and growth with no dysmorphic features, chromosomal abnormalities (e.g. fragile X syndrome) are unlikely. No hypopigmented macules are found on examination with Wood's lamp, ruling out neurocutaneous disorders. Note that it is important to rule out a hearing abnormality as the cause of delayed speech; this can be done with a frequency-specific auditory brainstem response. The score of 17 on the social communication questionnaire (SCQ, the cutoff for autism is >15) is further compatible with ASD. Magnetic resonance imaging (MRI) is not indicated in this case, as there is no history suggestive of neurological disease. Applied behavior analysis is the most important line of treatment for ASD. Risperidone, atomoxetine, or secretin are not indicated in the absence of aggressive or self-injurious behavior.


Discussion

Autism spectrum disorder (ASD) encompasses a wide continuum of associated cognitive and neurobehavioral disorders characterized by impaired socialization, impaired verbal and nonverbal communication, and restricted and repetitive patterns of behavior. Conditions on this spectrum are autism, Asperger syndrome, and "pervasive developmental disorder not otherwise specified". ASD is common, with an estimated prevalence of more than 1% in the United States. It has a 4:1 male predominance, suggesting a sex-linked etiology. The average age at diagnosis is six years, despite most parents noticing that 'something seems wrong' by 18 months of age and seeking medical attention by two years of age. The pathophysiology is not completely understood but is likely multifactorial, as noted by the heterogeneous group of disorders the term "ASD" encompasses. Genetics, maternal autoimmune disease, mitochondrial dysfunction, and environmental factors have been implicated, among others. A higher incidence is seen in patients with fragile X syndrome, Rett syndrome, obsessive-compulsive disorder, and tuberous sclerosis. Notably, siblings and twins of affected children have a higher incidence of the condition than the general population, which further points toward a genetic component. Common clinical features encountered in ASD include impairment of social communication and restricted or repetitive behaviors. There may be problems with eye contact, orienting to one's name, deficits in joint attention (where the child maintains focus on the same object as the examiner), pretend play, imitation, verbal and nonverbal communication, sensorimotor skills, and language development. Speech deficits are usually complex and may range from complete mutism to verbal fluency with errors in word meaning. Sensorimotor deficits may manifest as hypotonia, limb apraxia or stereotypical movements such as finger/hand mannerisms, rocking of the body, or assuming unusual postures. While there is no conclusive way to confirm or exclude autism based on neuropsychological impairments alone, certain tests, such as those of higher-order conceptual processing, reasoning, interpretation, abstraction may be helpful. Screening questionnaires with acceptable sensitivity and specificity include the Ages and Stages Questionnaire, BRIGANCE® Screens, or the Checklist for Autism in Toddlers (CHAT). Audiologic evaluation is recommended for all children from birth to 36 months with developmental delays; all types of hearing loss can co-occur with ASD. Appropriate laboratory investigations include genetic testing for chromosomal abnormalities, metabolic testing for inborn errors of metabolism, and electrophysiologic testing. The diagnosis is made using a tool with sufficient sensitivity and specificity like the Social Communication Questionnaire (SCQ) or the Social Responsiveness Scale (SRS), along with the DSM-5. Patients typically require ongoing medical and neurologic evaluations such as monitoring of cognitive and adaptive behavior, evaluation of sensorimotor deficits, and neuropsychological, behavioral, and academic assessments. Comprehensive programs for young children with autism include applied behavior analysis, a structured teaching approach focused on social skills development, occupational therapy, and sensory integration therapy in order to help patients cope with day to day activities and improve their quality of life. Patients should be offered standard preventive medical care, including immunizations. Pharmacologic interventions can be helpful in the presence of concomitant disorders of behavior, sleep, mood, seizures, or gastrointestinal problems.


Take home messages

  1. Autism spectrum disorder (ASD) is a heterogeneous group of conditions characterized by impaired socialization, impaired communication, and restricted and repetitive patterns of behavior.
  2. This group of disorders is associated with other organic brain conditions; the risk is increased in the presence of Rett syndrome, obsessive-compulsive disorder, fragile X syndrome, and tuberous sclerosis.
  3. The diagnosis should be made by screening with an accepted tool, apart from meeting the DSM criteria. Treatment should not be delayed even if the diagnosis is uncertain.
  4. ASD is incurable and generally lifelong. Comorbid cognitive impairment, medical problems, or the inability to care for oneself entail a poor prognosis.

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