Nystagmus 6, Congenital, X-linked
Patient Information
Characteristics
Background and History
Nystagmus, sometimes called ‘dancing eyes’ comes in many forms and has multiple causes. It may result from other eye disease or from more general neurological conditions. When present at birth (congenital), it is usually inherited in one of several patterns. Usually there is some reduction in vision since patients are unable to focus steadily on objects.
Clinical Correlations
The abnormal movement of the eyes may be noticed as early as 6 months of age. Vision is reduced to the range of 20/50 to 20/60. This is a stable condition and does not progress. Affected males have evidence of abnormal development of the central retina (macula) and the pigment of the retina appears irregular or ‘mottled’. Females do not have this condition. General health is normal.
Genetics
Inheritance
This is an X-linked disorder in which only males are affected. A father with this condition cannot pass it to any of his children but all his daughters will be carriers like their paternal grandmother. Carrier mothers can expect that half of their sons will have nystagmus and half of their daughters will be carriers like their mother. This pattern of inheritance is known as X-linked recessive.
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
Pediatricians and ophthalmologists are likely to make this diagnosis. It is important that complete physical and neurological examinations are done to rule out other conditions with which nystagmus is associated. Patients can look forward to a normal, healthy life. School children might benefit from the use of low vision aids.
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