OMIM ID:
Epileptic Encephalopathy, Early Infantile 48
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Poor eye contact is present from infancy. Optic atrophy has been reported in several patients and features of retinitis pigmentosa were present in sibs of one family.
Systemic Features
Infants usually present with hypotonia and feeding difficulties. Global developmental delay is also noted early and becomes more obvious with time. Seizures are often seen early and become intractable. Many individuals have microcephaly. Hypermobility with dyskinesias and hyporeflexia are often present. Speech is generally absent and many individuals are unable to sit or walk.
Brain imaging often shows atrophy of the cerebrum and cerebellum accompanied by enlarged ventricles and a thin corpus callosum.
Genetics
Inheritance
Homozygous or compound heterozygous mutations in the AP3B2 gene (15q25.2) can be responsible for this condition.
For another somewhat similar condition see early onset epileptic encephalopathy 28 (616211) with autosomal recessive inheritance. For an autosomal dominant condition with a similar clinical picture, see early onset epileptic encephalopathy 47 (617166).
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.