Bornholm Eye Disease
Patient Information
Characteristics
Background and History
Color vision defects may be inherited or acquired. This is a rare disorder of red-green color confusion associated with extreme nearsightedness and physical changes in the eye. The name is derived from the name of a Danish island where the first cases were found.
Clinical Correlations
Individuals are presumably born with high myopia (nearsightedness) and difficulty discerning red and green colors. It is a non-progressive disorder in which the vision remains good throughout life. The appearance of the retina is light in color suggesting that the usual pigmentation is absent and perhaps the optic nerve is abnormally small. The electrophysiologic test called an ERG shows that the cones (the cells of the retina that mediate color vision) are not functioning normally.
Genetics
Inheritance
The gene responsible for this disorder is located on the X chromosome but so far has not been identified further. Only males are affected and their mothers who carry the mutation on one of their two X chromosomes do not have evidence of disease (X-linked recessive). However they can expect on average that half of their sons will be affected. Males with this disorder do not transmit it to their children but all their daughters will receive the mutated X chromosome.
Pedigree
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.
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'.
Diagnosis and Prognosis
This is a stationary disorder with no evidence of progression of the myopia or colorblindness. There are no other health issues and longevity is normal. Ophthalmologists and vision scientists usually diagnose this disorder.
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