Retinoschisis, Juvenile
Patient Information
Characteristics
Background and History
The retina is divided into 8 microscopic layers, normally directly adjacent and connected to each other. Several conditions result when disease leads to a separation of these layers, called retinoschisis. This may cause some of the layers to malfunction which, of course, interferes with normal vision.
Clinical Correlations
Juvenile retinoschisis affects primarily the macula which is a special area of the retina that we use for our best vision. That is because this area contains the highest concentration of rods and cones, the cells that respond to light stimulation. The macula is located in the central portion of the retina which we use when focusing directly on visual targets (such as printed material). Therefore, any disease which interferes with normal functioning of this portion of the retina will lead to loss of good, sharp vision that we all depend upon for much of our daily activities. Small cysts can be observed in the macula where the layers are separated. The disease can also affect the more peripheral part of the retina and can sometimes cause a retinal detachment. When this separation occurs, blood vessels may be ruptured and the bleeding that follows may cause a sudden decrease in vision.
Genetics
Inheritance
Retinoschisis is caused by a genetic mutation in the RS1 gene that is located on the X-chromosome and is passed from parent to child. Since it is an X-linked recessive disorder, it occurs mainly in boys, who only have one copy of the X-chromosome in each cell. Females with two X chromosomes are affected only in rare cases. Females who are carriers of the mutated gene (the mutation is on only one of her X chromosomes) can transfer either the normal or abnormal X chromosome to each of the children. Thus, half of her sons will be affected and half of the daughters will be carriers. Affected males transfer the mutated gene to all daughters who become carriers like their paternal grandmother.
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
Juvenile retinoschisis usually presents in males during early childhood who complain of decreased vision and this cannot be corrected with glasses. The disorder can be diagnosed by an ophthalmologist by examination of the retina. The diagnosis can be confirmed by genetic testing of the RS1 gene, or by special retinal tests. The vision is highly variable, ranging from normal to very poor vision and it often worsens slowly with time. Treatment with dorzolamide for swelling in the macula can improve vision in some cases. Cataract may develop early on which can be treated with cataract surgery. Surgery may also help for retinal detachment and bleeding in the eye.
No treatment is available for the gene mutation.
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