OMIM ID:
Retinitis Pigmentosa 77
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
The onset of nyctalopia apparently varies from early childhood to 20 years of age and is usually the presenting symptom. The loss of acuity is progressive (20/30 to 20/400) with older patients generally having more severe loss but there is little direct correlation with age. Peripheral fields are progressively constricted, ranging from 10 to 30 degrees. Some patients develop posterior subcapsular cataracts. Retinal pigmentation is often mottled but ‘bone spicules’ are seen in about half of individuals. Retinal vessels are narrowed. The ERG shows generalized rod-cone dystrophy.
Systemic Features
No systemic abnormalities have been reported.
Genetics
Inheritance
Homozygous or compound heterozygous mutations in the REEP6 gene (19p13.3) are responsible for this disorder. Five unrelated families have been reported.
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.