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Pervasive Developmental Disorders (PDD): There are five disorders which fall under the umbrella of PDD, a category of neurological disorders characterized by "severe and pervasive impairment in several areas of development," including social interaction and communications skills (DSM-IV-TR)".  Each of these disorders has specific diagnostic criteria as outlined by the American Psychiatric Association (APA) in its Diagnostic & Statistical Manual of Mental Disorders (DSM-IV-TR).  

The five disorders are: Autistic Disorder, Asperger's Disorder, Childhood Disintegrative Disorder (CDD), Rett's Disorder, and PDD-Not Otherwise Specified (PDD-NOS).

  • Autistic Disorder (Autism): A complex developmental disability that appears during the first three years of childhood and continues through life. People with classical autism show three types of symptoms: impaired social interaction, problems with verbal and nonverbal communication, and unusual or severely limited activities and interests. These symptoms can vary in severity. In addition, people with autism often have abnormal responses to sounds, touch, and/or other sensory stimulation. Recent studies strongly suggest that some people have a genetic predisposition to autism. In some children, environmental factors may also play a role. Studies of people with autism have found abnormalities in several regions of the brain which suggest that autism results from a disruption of early fetal brain development. Autism and its associated behaviors have been estimated to occur in as many as 2:1,000 to 6:1,000 individuals (Centers for Disease Control and Prevention 2001). Autism is four times more prevalent in boys than in girls and it knows no racial, ethnic, or social boundaries. Family income, lifestyle, and educational levels do not affect the chance of autism's occurrence.
  • Asperger’s DisorderIn people with Asperger's Disorder, deficits in social interaction and unusual responses to the environment, similar to those in autism, are observed. Unlike in autism, however, cognitive and communicative development are within the normal or near-normal range in the first years of life, and verbal skills are usually an area of relative strength. Idiosyncratic interests are common and may take the form of an unusual and/or highly circumscribed interest (e.g., whales, the weather schedules, number of signs).
  • Childhood Disintegrative Disorder (CDD): Is a rather rare condition that has only recently been  'officially' recognized. With CDD children develop a condition which resembles autism but only after a relatively prolonged period (usually 2 to 4 years) of clearly normal development. CDD is characterized by a loss of skills occurring over time, and differs from autism in the pattern of onset and course. Although apparently rare, the condition probably has frequently been incorrectly diagnosed.
  • Pervasive Developmental Disorder, Not Otherwise Specified (PDD-NOS): Is a 'sub threshold' condition in which some - but not all - features of autism or another identified Pervasive Developmental Disorder are identified. PDD-NOS is often incorrectly referred to as simply "PDD." The term PDD refers to the class of conditions to which autism belongs. PDD is not in itself a diagnosis, while PDD-NOS is a diagnosis. The term Pervasive Developmental Disorder - Not Otherwise Specified (PDD-NOS; also referred to as "atypical PDD," or "atypical autism") is included in DSM-IV to encompass cases where there is marked impairment of social interaction, communication, and/or stereotyped behavior patterns or interest but when full features for autism or another explicitly defined PDD are not met.
  •  Rett's Disorder (Rett’s Syndrome): Is included as a Pervasive Developmental Disorder because there is some potential confusion with autism, particularly in the preschool years, otherwise the course and onset of this condition is very distinctive. Development appears normal until 6-18 months of age, followed by loss of acquired speech and hand skills, slowing of head growth, and development of stereotyped repetitive hand movements.  Motor problems are quite striking, and profound mental retardation is typical. While the DSM-IV does not list male sex in the exclusionary criteria, the existing literature on Rett’s Disorder documents the condition occurring primarily in girls.  Rett’s Disorder is thought to occur from 1:10,000 to 1:23,000 female births.
Additional Disorders that apparently overlap with or may occur along with autism:
  • Angelman Syndrome (AS): A rare neuro-genetic disorder and the prevalence rate requires further study.  Current literature estimates a prevalence among children and young adults of between 1:10,000 to 1:20,000 individuals.   AS is characterized by severe intellectual disability, speech impediment, sleep disturbance, unstable jerky gait, seizures and usually a happy demeanor.  Although it is not considered a subtype of autism, individuals do exhibit many behaviors characteristic of autism and are sometimes given a secondary diagnosis of autism.  Persons with AS share common facial features, such as a wide smiling mouth, a thin upper lip, and deep set eyes. More than half have low levels of pigmentation in their eyes, hair, and skin.  In contrast to autism, people with Angelman syndrome are often described as very sociable. They are very affectionate and engage in frequent laughing.
  • Fragile X Syndrome, also called Martin-Bell Syndrome, is a genetic disorder and is the most common form of inherited mental retardation. It is a sex-linked genetic abnormality in which the mother is a carrier, transmitting the disorder to her sons. It affects approximately 1:1,000 to 1:2,000 male individuals, and the female carrier frequency may be substantially higher. Males afflicted with this syndrome typically have a moderate to severe form of intellectual handicap. Females may also be affected but generally have a mild form of impairment. Approximately 15% to 20% of those with Fragile X syndrome exhibit autistic-type behaviors, such as: poor eye contact, hand-flapping or odd gesture movements, hand-biting, and poor sensory skills. Behavioral problems and speech/language delay are common features of Fragile X syndrome.  People with Fragile X syndrome also have a number of recognizable physical features, including a high arched palate, strabismus (lazy eye), large ears, long face, large testicles in males, poor muscle tone, flat feet, and sometimes mild, heart valve abnormalities. Although most individuals with Fragile X syndrome have a characteristic 'look' (long face and large ears), there are some who do not have typical features. Many hospitals and laboratories perform blood tests to diagnose Fragile X syndrome.
  • Prader-Willi Syndrome (PWS): A disorder which is sometimes associated with, but not a subtype of, autism. The classical features of this disorder include an obsession with food which is often associated with impulsive eating, compact body build, underdeveloped sexual characteristics, and poor muscle tone. Because of their obsession with food, many people afflicted with Prader-Willi syndrome are overweight. Most individuals with Prader-Willi syndrome have mild mental retardation.   Some of the behaviors which are common to both Prader-Willi syndrome and autism are: delays in language and motor development, learning disabilities, feeding problems in infancy, sleep disturbances, skin picking, temper tantrums, and a high pain threshold.  Prader-Willi syndrome affects approximately 1 in 10,000 people. Most individuals suffering from this disorder are missing a small portion of chromosome 15 which appears to come from the paternal side of the family; when the portion of chromosome 15 comes from the maternal side, the person may suffer from Angelman syndrome.

 

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