Cataracts, Congenital, with Intellectual Disability
Defective Genes
Clinical Characteristics
Ocular Features
Reported patients have bilateral posterior polar lens opacification, presumably present since birth. No other ocular abnormalities are present. Vision is stated to be normal following early cataract extractions. No glaucoma has been detected while spectral OCT and electrophysiological studies had normal results.
Systemic Features
Psychomotor disabilities and developmental delays are present. Walking does not occur until the age of about 2 years and speech is present by 5 years. No dysmorphic features or other organ disease are present. MRI studies of the brain are normal.
Genetics
Inheritance
This is an autosomal recessive disorder resulting from homozygous mutations in the STX3 gene (11q12.1). It has been reported in three children in a consanguineous Tunisian family.
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.