OMIM ID:
Retinitis Pigmentosa 76
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Onset of night blindness occurs early in the second decade of life. Vision is in the range of 20/40 to 20/100 in the first decades worsens slowly but there is a wide range. Some older individuals may have hand motion vision in at least one eye but some retain 20/40. All patients have peripheral field restrictions and some have pallor of the optic disc. Retinal vessels are attenuated. Fundus pigmentation is usually abnormal with some combination of bone spicule and diffuse salt and pepper pigmentation. The macula is usually involved with a flat fovea, cystoid macular edema, and chorioretinal atrophy.
Retinal thinning is seen on OCT. The ERG can be flat but in some individuals the rod responses are primarily reduced.
Systemic Features
No systemic abnormalities have been associated.
Genetics
Inheritance
Homozygous or compound heterozygous mutations in the POMGNT1 gene (1p34) are responsible for this disorder.
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.