What is Deafblindness?
Presentation of Features
Pattern of Inheritance
World-wide Distribution of Alström Syndrome
Alström Syndrome (AS) was first described by Carl Henry Alström of Sweden in 1959 in a paper he co-authored with B. Hallgren, I.B. Nilsson and H. Asander1 . Alström Syndrome is a hereditary and very rare, life threatening disorder which begins to take effect during early childhood. At present there are 104 children and adults world-wide known to have this condition which can be quite variable and have an age-related progression.
Alström Syndrome is autosomal recessive and even though it has been mapped to chromosome 2p13, the gene responsible for the disorder has not been identified. Prenatal tests are not available for Alström Syndrome but diagnosis is made when particular features of the syndrome are observed.
In clinical medicine, diagnosis is made when four out of five principal features of AS are present. These are degeneration of the retina (retinopathy) at an early age i.e. under 1 year, which is usually first noticed as involuntary eye movements (nystagmus) and/or light sensitivity (photophobia). In addition, infantile obesity, cardiomyopathy (infantile or adolescent), mild to moderate sensorineual hearing loss may also be observed in early childhood, and type 2 diabetes mellitus or high levels of insulin in the blood (hyperinsulinemia) usually begin in adolescence.
PRESENTATION OF FEATURES
Alström Syndrome tends to progress in a particular order with one of the first signs being either infantile dilated cardiomyopathy and/or nystagmus and photophobia. Both can occur as early as 1-3 weeks of age. Obesity is usually seen beginning in the first year or two of life. Hyperinsulinemia/insulin resistance has been documented in children as young as 2 years old, but there is not a lot of information about this yet. Sensorineural hearing loss occurs at approximately 4 - 6 years of age, diabetes may develop, usually after adolescence There may be kidney and liver problems too.
PATTERN OF INHERITANCE
Alström syndrome is autosomal recessive which means that for a child to have the condition they must inherit one mutated gene from their mother and one from their father (see diagram).
Diagram to show pattern of inheritance for Alström Syndrome:
As the diagram shows, for each pregnancy there is a probability of 25% that
parents who are carriers of the mutated gene will have a child with Alström
syndrome. There is also a probability of 25% of having an unaffected child who
will not be a carrier and a probability of 50% that they will have unaffected
children who are carriers of the gene. Boys and girls have an equal chance of
inheriting the gene responsible for Alström syndrome.
In 1997 researchers at the Jackson Laboratory in Bar Harbor, Maine, USA located the gene for Alström syndrome on chromosome 2. Genetic research is being conducted world-wide to identify the mutation responsible for such devastating effects on multiple organ systems. Research is also taking place in Canada, United States of America, France, Italy and the United Kingdom.
Children with Alström syndrome can and do lead full and productive lives. Even though there is no cure for Alström Syndrome treatment/therapy is possible to alleviate some of the symptoms experienced by those that have the condition. For instance, diabetes mellitus may be controlled with medication combined with diet and exercise, and the use of hearing aids can help children and adults cope with hearing loss.
WORLD-WIDE DISTRIBUTION OF ALSTRöM SYNDROME
As stated earlier there are 104 known children and adults with Alström syndrome who live in 16 different countries around the world. Most of these are in developed countries such as Canada, the United States of America and the United Kingdom - the latter having the largest group of diagnosed AS children and adults.
The distribution of Alström Syndrome affected individuals mostly seen in developed countries highlights the concern that there are probably many more AS cases in developing countries going undiagnosed, and this may be attributable to lack of information about the syndrome. Undiagnosed children could be missing out on vital medical treatment and educational approaches appropriate to their needs.
The Jackson Laboratory, Maine, USA is currently leading the research into identifying the genetic mutation. The international Society for Alström Syndrome Families (SASF) is also based in Maine, USA and has a board of directors consisting of people from Canada, USA and the UK. Branches are located elsewhere within the United States and one has recently established in the United Kingdom while another is just being formed in Canada.
The Jackson Laboratory
600 Main Street
Maine 04609 - 1500
14 Whitney Farm Road
Mount Desert, Maine 04660
Alström Syndrome - UK
49 Southfield Avenue
England, UK. TQ3 1LH
Alström Syndrome - Canada
World Wide Web Information
Sense, November 1999.