Aland Island Eye Disease
Patient Information
Characteristics
Background and History
This is a rare disorder of the eye first described in 1964 in a large family of Norwegian descendents on the island of Aland in the Bothnian Sea. Males are primarily affected but females may have mild symptoms as well. It has interesting similarities to a type of albinism and a form of congenital stationary night blindness also occurring primarily in males.
Clinical Correlations
Males with this disorder may experience severe, progressive near-sightedness, ‘dancing eyes’, a specific form (protan) of color blindness and decreased ability to see at night. Some patients have decreased pigmentation in the retina and iris. Malformation of the retina structures may result in a mild to severe decrease in vision. Carrier females in this X-linked disorder may have minor eye disease as well with subtle color vision changes and changes in eye movements.
No consistent systemic abnormalities have been reported.
Genetics
Inheritance
This is an X-linked recessive disorder, so called because the responsible mutation is in a gene on the X chromosome. Since males have only one X chromosome, there is no ‘normal’ X chromosome to counterbalance the harmful effects of the single gene change and they have the most serious clinical disease as noted above. Occasional females whose mutant X chromosome may be more active can also have mild disease. Since males pass on only their Y chromosome to their sons, none will have this eye disease but the single mutant X chromosome goes to all daughters so they become obligatory carriers with the potential to have affected sons.
Pedigree
X-linked recessive, carrier mother
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the mother, she usually does not have the disease since the normal X chromosome without the mutation neutralizes the mutation in the abnormal X chromosome. However, half her sons will inherit the mutation-containing X chromosome and therefore have the X-linked disease. Half the daughters will inherit the mutation-bearing X chromosome and are usuallly healthy 'carriers'.
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the mother, she usually does not have the disease since the normal X chromosome without the mutation neutralizes the mutation in the abnormal X chromosome. However, half her sons will inherit the mutation-containing X chromosome and therefore have the X-linked disease. Half the daughters will inherit the mutation-bearing X chromosome and are usuallly healthy 'carriers'.
X-linked recessive, father affected
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the father, he has the disease since his only X chromosome is mutant and he has no normal X to blunt the effects of the abnormal gene. His sons only receive his Y chromosome and thus are all normal. However, all his daughters receive his one and only X chromosome and will be healthy 'carriers'. Thus such males will have no affected children but half their grandsons from those daughters will have the same disease as he does.
X-linked disorders are caused by a mutation on the X chromosome and both sexes can pass this to their children. If the mutation is in a recessive gene and carried by the father, he has the disease since his only X chromosome is mutant and he has no normal X to blunt the effects of the abnormal gene. His sons only receive his Y chromosome and thus are all normal. However, all his daughters receive his one and only X chromosome and will be healthy 'carriers'. Thus such males will have no affected children but half their grandsons from those daughters will have the same disease as he does.
Diagnosis and Prognosis
The diagnosis may be suspected in males by an eye doctor who finds the characteristic symptoms and signs. However, the clinical similarities between Aland Island Eye Disease and X-linked forms of night blindness and albinism, other studies such as electroretinograms and gene studies may be necessary to rule out other disease. The only treatment is correction of the near sightedness with glasses and contact lenses. The use of low vision aids can also be helpful.
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