Rare chromosome disorders

Prader-Willi and Angelman syndromes are rare genetic conditions both caused by irregularities in chromosome 15. They aren’t diseases, but are neurological disorders which can cause severe learning difficulties.

Williams syndrome is a non-hereditary chromosone disorder. 

Learning difficulties may make mainstream education problematic, but a child may lack the stimuli of verbal communication and social interaction if placed in a special school.

Angelman syndrome

Children with Angelman syndrome (AS) used to be termed ‘puppet children’ because of their characteristic happy demeanour, small head, sometimes inappropriate laughter and stiff jerky movements.

They also have a tendency to extreme thinness. Other characteristics include sleep problems, lack of speech (greater receptive than expressive language), and developmental delay. To date only about 350 cases have been diagnosed in the UK. Some children with AS have been wrongly diagnosed as having an autistic spectrum disorder or cerebral palsy.

Prader-Willi syndrome

Prader-Willi syndrome (PWS) is often characterised by an insatiable appetite for food and tendency to gain weight very rapidly, often leading to serious obesity and associated medical problems.

Characteristics include: poor muscle tone, co-ordination and balance; emotional and social difficulties; immature physical development; immature development of sexual organs (few reach full sexual maturity); and possibly learning difficulties. As with Down’s syndrome, many people with PWS also exhibit characteristic facial and other physical features. These include small hands and feet, almond-shaped eyes, a narrow forehead and a down-turned mouth with a triangular-shaped upper lip.

There is no cure for PWS, although some aspects can be treated. The Prader-Willi Syndrome Association UK recommends the help of a dietitian, paediatrician, physiotherapist, educational psychologist and (if necessary) speech therapist should be sought as soon as a diagnosis is made.

Williams syndrome

Williams syndrome is a rare, non-hereditary chromosome disorder which occurs at random and affects intellectual development. There may be associated physical problems ranging from slight muscle weakness to heart defects.

Each sufferer has a unique set of physical, emotional and mental strengths and weaknesses, which need to be monitored and understood by those caring for the sufferer.

As with Down’s syndrome people may have a facial similarity. They are characterised by ‘elfin’ features – a wide mouth, turned-up nose with flattened bridge, slightly puffy cheeks and widely spaced irregular teeth. Some may have a squint. Initial signs of Williams syndrome include low birth weight, slow weight gain, below average growth, missing developmental milestones, slow feeding, restlessness, hyperactivity and possible excess vomiting. A raised calci...