Chorioretinopathy, Ataxia, and Hypogonadism
Patient Information
Characteristics
Background and History
The association of retinal and neurological disease is common in this rare inherited disorder. This combination may also be associated with disorders of sexual organs or function.
Clinical Correlations
The first symptoms may appear in late childhood when reduced vision, night blindness, and constriction of the visual fields are noted. Some patients are abnormally light sensitive. However, the onset is highly variable and many patients are not diagnosed until they are young adults when secondary sexual characteristics fail to develop. Young children may be aware of some ‘clumsiness’ but gait and balance difficulties (ataxia) become increasingly apparent in early adulthood. Tremors in the hands and abnormal speech are often present. Progression of symptoms is highly variable.
The retina in the back of the eye has changes in the pigment layer and test of its function using the electroretinogram (ERG) reveals subnormal responses to light. Some patients have nystagmus (‘dancing’ or jerky eye movements). Color vision is often only moderately impaired.
Genetics
Inheritance
This likely is an autosomal recessive disorder requiring the presence of mutations in both copies of a gene. In this case, parents who carry as single copy of the abnormal gene are normal but each of their children have a 25% risk of inheriting the mutation from both parents.
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.
Diagnosis and Prognosis
The diagnosis requires the combined expertise of ophthalmologists, neurologists, and endocrinologists. Hormonal therapy can stimulate the development of secondary sexual characteristics and may restore reproductive function. Several women have given birth after hormone substitution therapy.
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