OMIM ID:
Pontocerebellar Hypoplasia 11
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Some patients are reported to have poor eye contact, hyperopia, and strabismus. Three individuals had colobomas. Strabismus, poor eye contact, and hyperopia have been noted in some individuals.
Systemic Features
Microcephaly and large ears may be noted at birth. Some patients have general hypotonia while others have spastic hypertonia. Neurological features include markedly delayed psychomotor development, truncal and appendicular ataxia, and cognitive delays. Developmental milestones such as walking, sitting, and speech are delayed. Some patients have seizures. A variety of behavior abnormalities have been reported including stereotypical movements, autistic behavior, repetitive motor movements, and poor communication. Dysarthria and dysphagia are sometimes present. There seems to be little progression of the neurological manifestations.
Brain MRIs reveal cerebellar hypoplasia and hypoplasia or agenesis of the corpus callosum in most patients.
Genetics
Inheritance
Homozygous mutations in the TBC1D23 gene (3q12.1q12.2) cause 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.