OMIM ID:
Keratoconus Posticus Circumscriptus
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
The posterior corneal surface has area(s) of excavation (indentation) associated with overlying opacification. The lens-corneal separation is reduced and iridocorneal adhesions are often present. The clinical picture has been described as ‘posterior conical cornea’ or posterior keratoconus.
Systemic Features
The neck is short and has webbing. The facies appear ‘coarse’, the posterior hairline is low, the nose is prominent, digits are short, and the vertebral anomalies may lead to scoliosis. Individuals are short of stature and brachydactyly is often present. Developmental delays and mental retardation are usually features. Other variable anomalies have been reported.
Genetics
Inheritance
Autosomal recessive inheritance seems most likely in view of the family patterns. Based on the few families reported, it is uncertain if this is a single entity with variable expression or a combination of disorders. No gene or locus has been associated with this condition.
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.