OMIM ID:
Infantile Cerebellar-Retinal Degeneration
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Visual tracking can be normal during the newborn period but lack of visual fixation and attention soon become evident. Strabismus, nystagmus, and abnormal pursuit movements are often present. Optic atrophy has been reported as early as 3 years of age. VEP and ERG responses are extinguished in the first two years. The nystagmus may be multidirectional. Acuity loss seems to be progressive. A progressive retinal degeneration (not further characterized) has been reported.
Systemic Features
Infants generally appear normal at birth. Within the first 6 months they show signs of developmental delay and neurological signs such as truncal hypotonia, seizures, athetosis and head bobbing. Milestones of sitting, rolling over, and reactions to others are seldom achieved. Cerebellar brain imaging shows progressive atrophy in all patients and some have cortical atrophy as well. Some patients have evidence of hearing loss. Severe failure to thrive and psychomotor delays are usually present. Death may occur within several months of birth although some live for several decades.
Genetics
Inheritance
This condition results from homozygous or compound heterozygous mutations in the ACO2 gene (22q13.2). The mutation has also been associated with optic atrophy 9 (616289).
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.