OMIM ID:
Macular Dystrophy with Central Cone Involvement
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
This is primarily a cone dystrophy but there is evidence of some rod damage in older patients. A mild decrease in central acuity is noted by individuals in the third to sixth decades. Slight pigmentary changes and color vision abnormalities can be documented with the onset of these symptoms and a bull’s eye maculopathy and severe atrophy of the central fovea may be present. An enlarging central scotoma with normal periphery can sometimes be identified. Other patients have an atrophic appearance to the peripapillary area with a pale optic disc. ERG responses to full-field testing are normal but multifocal studies reveal severely reduced central responses.
Systemic Features
No systemic abnormalities have been reported.
Genetics
Inheritance
Compound heterozygosity for a missense mutation and a nonsense mutation in the MFSD8 gene (4q28.2) has been found among members of a Dutch sibship suggesting autosomal recessive inheritance.
The same mutant gene has been identified in some patients with late infantile or early juvenile onset lysosomal storage disease known as neuronal ceroid lipofuscinoses (610951) in which there may be optic atrophy, attenuated retinal vessels, a pigmentary retinopathy, and severe vision loss. However, it is of note that no members of the Dutch family with the macular cone dystrophy described here had extraocular manifestations.
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.