Clinical Characteristics
Ocular Features
This is a rare syndrome consisting of a pigmentary degeneration of the retina in association with nanophthalmos. The globe is small with a thickened choroid and sclera and the macula becomes atrophic later in life. Some patients have cystic macular changes early without fluorescein leakage. The anterior chamber is shallow, the angle is narrow, and the cornea may be small leading to angle closure glaucoma in most patients. Extensive anterior and posterior synechiae can be seen. The retina has a postequatorial bone spicule pattern of pigmentation with narrowing of arterial vessels. Hyperopia is usually present and nightblindness may be noted in the first decade of life. The ERG early shows loss of rod function and progression of the retinal disease subsequently leads to extinction of all rod and cone responses by midlife. The EOG may be subnormal and visual fields are severely constricted. Pallor and crowding of the optic nerve are common. The vitreous may contain prominent fibrils and fine white granules. Visual acuity is often 20/200 or worse.
Systemic Features
No systemic abnormalities have been reported.
Genetics
Inheritance
This is likely an autosomal recessive disorder based on frequent parental consanguinity and sibships with multiple affected individuals of both sexes. However, the first reported family in 1958 with 13 affected individuals in 4 generations suggested autosomal dominant inheritance. No molecular defect has been identified.
This may be the same disorder as microphthalmia with retinitis pigmentosa (611040) in which so far no molecular mutation has been identified.
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.