OMIM ID:
Optic Atrophy 6
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Visual impairment is often noted under the age of 6 years. The disease is bilateral and loss of vision procedes slowly, eventually reaching 20/100 to 20/200. Moderate photophobia and dyschromatopsia are present but nystagmus is absent. The impact on the visual field seems to be minimal and limited to decreased sensitivity in the central areas.
Systemic Features
No systemic abnormalities are associated.
Genetics
Inheritance
Evidence for this presumed autosomal recessive type of optic atrophy is based on a single large, consanguineous French Canadian family. A locus in the 8q21-q22 region presumably containing the mutant gene, designated OPA6, was found. Linkage analysis excluded genes linked to autosomal dominant optic atrophy.
Another autosomal recessive optic atrophy disorder (OPA7; 612989) has also been reported.
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.