OMIM ID:
Cataracts, Congenital Zonular Pulverulent 1
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Bilateral lens opacities may be both nuclear and zonular. The embryonic and fetal nuclei are usually involved and diffuse cortical opacities may also be seen in some patients. The involved area is therefore larger than the somewhat similar Coppock-like cataract (604307) which is limited to the embryonic nucleus. The lens opacities may be seen at birth or in early childhood and usually progress. There is considerable clinical variation in the degree and distribution of the usual dust-like opacities which may also be lamellar in distribution with a clear peripheral cortex and minimal nuclear involvement. Microcornea has also been reported. In mild cases the lens opacities are primarily clustered along the Y sutures resembling congenital zonular cataracts with sutural opacities (600881).
Three unrelated patients with mutations in GJA8 and total sclerocornea have been reported. Two of these patients in addition had small abnormal lenses while the third had cataracts and micropthalmia. Two of the three also develped glaucoma by one year of age.
The nature and morphology of the lens opacities in an adult have been studied by light and scanning electron microscopy. They are located in the embryonic and fetal nuclei and appear "puffy" with lens fiber irregulaties and entanglement in adjacent areas.
Systemic Features
None.
Genetics
Inheritance
Congenital zonular pulverulent cataracts are inherited in an autosomal dominant pattern resulting from missense mutations in the GJA8 gene (1q21.1) that codes for connexin 50. These belong to a category of lens opacitites now designated "Cataract 1, Multiple Types" in OMIM (116200). They have been detected in multiple populations and ethnic groups around the world.
Mutations in CZP3 at 13q11-13 coding connexin 46 (601885) result in a similar phenotype (Cataracts, Congenital Zonular Pulverulent 3) suggesting that genetic heterogeneity is present.
This was the first disease locus to be linked on a human autosome, in this case to the Duffy blood group locus on chromosome 1.
Pedigree
Autosomal dominant
Autosomal dominant disorders require only one mutation for the disease to be expressed. Since an affected parent has two chromosomes, only one of which has the mutant gene, parents can expect that half (50%) of their children will receive that one and inherit the disease. It is common for individuals that inherit the mutation, however, to not have evidence of the disease (nonpenetrance).
Autosomal dominant inheritance leads to a vertical pattern of transmission