OMIM ID:
Retinal Dystrophy with or without Macular Staphyloma
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Few patients have had complete eye studies and physical findings are seemingly limited to the eye. Patients complain of progressively decreasing vision as early as the first decade of life. Abnormal retinal findings may be present by the second decade and maybe earlier. The RPE can appear mottled and the retinal vessels are attenuated. Retinal pigment clumping occurs later. Night blindness and visual field constriction occur. Cone and flicker ERGs may be nonrecordable while rod and flash ERGs are reduced consistent with a rod-cone dystrophy. The retinal lamination has been described as abnormal on OCT in some individuals.
Macular staphylomas have been described in three unrelated offspring of consanguineous parents.
Vision loss is severe with legal blindness by midlife and one patient lost light perception by 40 years of age.
Systemic Features
No consistent systemic abnormalities have been reported.
Genetics
Inheritance
Homozygous or compound heterozygous mutations in the C21orf2 gene (21q22.3) are the cause of this autosomal recessive syndrome.
Homozygous or heterozygous mutations in the same gene are responsible for axial spondylometaphyseal dysplasia (602271).
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.