Chromosomal Disorders

Chromosomal duplications, deletions and abnormalities are determined by genetic testing undertaken by a qualified medical practitioner known as a geneticist.

Chromosomal disorders and autism

It is possible for a child with identified chromosomal abnormalities to receive another diagnoses (e.g., pervasive developmental delay or autistic spectrum disorder). The common characteristic that affects the majority of children with chromosomal disorders is significant learning disability and developmental delay. Chromosomal disorders of the 7th, 11th and 15th have all been implicated in the development of autism.

Each child is unique and will continue to develop at his or her own pace. However, particular chromosomal disorders sometimes lead to a diagnosis of a particular syndrome.

The x-linked MecP2 transformation is specific to Rett Syndrome and seen only in girls
The chromosome 21 trisomy is specific to Downs Syndrome
Duplications on the 15th chromosome is referred to as Isodicentric 15 or IDIC 15
A weakening on the one arm of the x chromosome, the FMR-1 gene, results in Fragile-x Syndrome.

Fragile-X Syndrome

Children with fragile-x have severe intellectual impairment, hyperactivity, short attention span and perserverative speech. They are often tactile defensive (avoid touching surfaces) and exhibit hand-flapping or hand-biting. Physical features include hyperflexible joints, large or prominent ears, and large testicles. The palm of the hand reveals a Simian crease or Sydney line (line frome one side to the other). Children with fragile-x syndrome do not make good eye contact.

Links between Autism and Fragile-X Syndrome

Fragile x is the most common known cause of autism. Aproximately one-third of children diagnosed with Fragile X syndrome will also have autism. Between 2-6% of children with a primary diagnosis of autism, the cause will be the Fragile X mutation.

Isodicentric 15th Chromosome (idic15)

Children with idic(15) are typically born with 47 chromosomes in each of their body cells, instead of the usual 46. It is the presence of this extra genetic material that is thought to account for the symptoms seen in some people with idic(15). Typical feaures include: Poor muscle tone (hypotonia), delayed milestones, intellectual disabilities, autism spectrum disorders, seizure disorders, speech/language delay, sensory processing disorders, attention deficit disorders (ADD/ADHD), anxiety disorders, minor unusual physical features, including wide-spaced eyes with skin folds at the inner corners (epicanthal folds); noticeable unfolding of the edge of the ears; short, upturned nose with a low or flattened nasal bridge; and full lips. Often children with idic15 are strikingly beautiful.

A small group of children and adults with idic15 have the very specific and well-known disorders called Prader-Willi syndrome (PWS) and Angelman syndrome (AS).

Angelman's Syndrome

Angelman Syndrome (AS) is a genetic neurological disorder in which a characteristic facial appearance is associated with severe developmental delay or mental retardation, difficulties with verbal communication, movement or balance disorders, and unique behaviour that sometimes includes unusual expression of emotion, hand-flapping movements and a short-attention span. It is thought to be caused by a genetic disorder relating to a deletion of a certain gene located on the 15th chromosome.

Prada Willi Syndrome

Prada Willi Syndrome (PWS) characteristics include feeding problems and poor weight gain in infancy; excessive or rapid weight gain between 1 and 6 years of age; central obesity in the absence of intervention; distinctive facial features (diolichocephaly in infants, narrow face/bifrontal diameter, almond-shaped eyes, small-appearing mouth with thin upper lip and down-turned corners of mouth); hypogonadism (genital hypoplasia, including undescended testes and small penis in males); delayed or incomplete gonadal maturation and delayed pubertal signs after age 16, including scant or no menses in women; global developmental delay before age 6; mild to moderate mental retardation or learning problems in older children; hyperphagia /food foraging/ obsession with food; and characteristic behaviour problems, such as temper tantrums, violent outbursts, obsessive/compulsive behaviour; perseveration (possessive and stubborn, repeating or fixating on one method or one point of interest); and show a tendency to be argumentative, oppositional, rigid, and manipulative.