Nanophthalmos Plus Syndrome
Patient Information
Characteristics
Background and History
Several gene mutations result in eyeballs (globes) that are either larger or smaller than normal. In nanophthalmos, the globe is smaller than average and for some, but not all patients there can be problems in the retina as well.
Clinical Correlations
This type of nanophthalmos is called plus syndrome because it has associated retinal and optic nerve problems as well. Nightblindness occurs in childhood along with mildly decreased general vision. It is a progressive disorder and eventually all retinal receptors become dysfunctional with legal blindness (20/200) resulting. Peripheral (side) vision becomes severely restricted. There is also crowding of the eye structures which increases the risk of acute glaucoma attacks although this seems to be less likely than in some other forms of nanophthalmos. The optic nerve has unusual deposits which are visible but do not seem to cause problems. There are no abnormalities in other parts of the body.
Genetics
Inheritance
This is an autosomal recessive disorder in which most cases are the offspring of related parents (horizontal pattern). It is not passed from parent to child.
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
Diagnosis and Prognosis
Only an ophthalmologist can diagnose this disorder and distinguish it from some similar conditions. The risk of acute glaucoma must be assessed by periodic eye examinations. Vision is always subnormal but complete blindness has not been reported. Most problems are due to constriction of side vision and difficulties seeing in low light. Low vision aids could be helpful.
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