OMIM ID:
Retinitis Pigmentosa, Deafness, Mental Retardation and Hypogonadism
Defective Genes
Clinical Characteristics
Ocular Features
Only two families with this presumed disorder have been reported. The retinal picture resembles retinitis pigmentosa with ‘bone spicule’ pigment clumps, vascular attenuation, and pale optic nerve heads. Cataracts and nystagmus have been observed. Vision is usually limited to light perception by the middle of the first decade of life.
Systemic Features
Small testes and gynecomastia are found in males while females have oligo- or amenorrhea. The hands and feet appear broad and the face has a coarse appearance with a depressed nasal bridge and a broad nose. Insulin-resistant diabetes and hyperinsulinemia are present. Acanthosis nigricans, keloids, obesity, and hearing loss are also features. All patients have significant developmental delays and evident mental retardation.
Genetics
Inheritance
No locus has been identified although autosomal recessive inheritance seems likely: the parents in one family were first cousins and there was no parent to child transmission.
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.