OMIM ID:
Microcephaly 20, Primary, Autosomal Recessive
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Microphthalmia and optic nerve hypoplasia with “blindness” seem to be common.
Systemic Features
Short stature and global developmental delay are usually present. Poor or absent speech is characteristic and intellectual disability may be severe. Few individuals can walk. Foot deformities and hypotonia are often present. Behavior problems are common having features of ADHD, autism, and aggression. Foot deformities have been noted.
Imaging of the brain may reveal cerebellar hypoplasia, a simplified gyral pattern, and absence of the corpus callosum.
Genetics
Inheritance
Homozygous or compound heterozygous mutations in the KIF14 gene (1q32.1) are responsible for this disorder.
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.