Chorioretinopathy with Microcephaly 3
Patient Information
Characteristics
Background and History
This is one of several rare and ill-defined genetic conditions in which infants born with below average head size also have abnormal eye development that primarily involves the retina.
Clinical Correlations
The below normal head size may be noted at birth. During childhood some patients develop nystagmus (wandering eye movements) indicating subnormal vision. Examination of the retina reveals severe disorganization with loss of normal pigmentation and blood vessels. Testing with an electroretinographic machine (ERG) may reveal severe malfunction of the rods and cones. Folds may develop in the retina and progress to a retinal detachment.
Motor skills and general development for the most part are normal. Speech delays are mild and mental function is normal or near normal. Brain imaging may reveal mild anomalies.
Genetics
Inheritance
This can be considered an autosomal recessive condition that requires two mutations in the same gene. Each clinically normal parent contributes one and such carrier parents can expect that 35% of their children will have 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.
Diagnosis and Prognosis
The diagnosis is usually based on a collaborative effort by pediatricians, geneticists, neurologists, and ophthalmologists. There is no specific treatment but physical therapy, special education, and low vision aids can be helpful.
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