OMIM ID:
Cataracts, Congenital with Sclerocornea and Glaucoma
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
The ocular features are evident at birth or within the first year of life and may be asymmetrical. The phenotype is heterogeneous but does not appear to be progressive. The anterior chambers are of normal depth and the fundi are normal when visualization is possible. The corneal opacification is usually denser peripherally and resembles corneoscleralization but it can extend centrally to a variable degree. In individuals with glaucoma and buphthalmos the cornea is more opaque and usually vascularized. In such eyes the cornea is thinned. In most patients the corneal diameters were 5-8 mm in diameter but in those with elevated pressures the anterior segment was obviously buphthalmic. Iridocorneal adhesions may be present. The lenses are cataractous but the capsules are normal. Microphthalmia has been reported in some patients. Vision is often in the range of hand motions.
Systemic Features
None.
Genetics
Inheritance
Homozygous mutations in PXDN (2p25.3) encoding peroxidasin are believed responsible for this autosomal recessive condition. Mammalian peroxidasin localizes to the endoplasmic reticulum but is also found in the extracellular matrix and is believed important to the maintainence of basement membrane integrity. The protein is one of several that aids in the extracellular breakdown of hydrogen peroxide and free radicals. In mouse eyes it localizes to the corneal and lens epithelium but its role in maintaining transparency of the lens and cornea is unknown.
See also Cataracts, Congenital Zonular Pulverulent 1 (116200) in this database for a condition with a similar phenotype but caused by heterozygous mutations in the GJA8 gene.
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.