OMIM ID:
Retinitis Pigmentosa 71
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Night blindness is noted in the first or second decades of life. The fundus picture in this condition resembles classic retinitis pigmentosa with attenuated vessels, RPE anomalies with bone spicule clumping and areas of atrophy, and optic disc pallor. Several patients had optic nerve drusen. The retina appears to have microcysts, especially in the macula, and the outer retina is thinned.
Systemic Features
Only a few patients have been reported with this form of RP and the full phenotype is unknown. Some individuals are obese and one patient in addition had postaxial polydactyly and hypercholesterolemia suggestive of a Bardet-Biedl-like phenotype. No reported patients have had rib dysplasia.
Genetics
Inheritance
Homozygous or compound heterozygous mutations in the IFT172 gene (2p23.3) have been identified in this condition.
The same gene is mutated in the recessive short-rib thoracic dysplasia 10 syndrome with or without polydactyly (615630). Individuals with the short-rib syndrome may have night blindness and fundus changes resembling retinitis pigmentosa.
Because of the phenotypic overlap with other conditions such as Bardet-Biedl syndrome, the short-rib thoracic 10 syndrome (615630), Majewski syndrome (263520), Jeune syndrome (208520), short-rib thoracic dysplasia 9 (266920), and certain types of polycystic diseases of the kidney with abnormalities of the cilia, it has been suggested that RP71 should be classified as a syndromic ciliopathy.
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.