OMIM ID:
Brown-Vialetto-Van Laere Syndrome 2
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Decreased vision, optic atrophy, and nystagmus are frequently present. Pupillary reflexes may be absent.
Systemic Features
Rapidly progressive muscle weakness and ataxia present in childhood. Early development may be normal but the first symptoms usually appear by age 2 or 3 years of age. Cognition is usually normal. Exercise intolerance soon appears along with dysphonia, dyspnea, dysphagia, and weakness of shoulder, neck and axial muscles. Wasting and weakness of hand muscles is often noticeable. Kyphoscoliosis, tongue fasciculations, and areflexia are often seen. Sensorineural hearing loss is a common feature.
Death from respiratory insufficiency often occurs within a few years after onset.
Genetics
Inheritance
Homozygous mutations in the SLC52A2 (8q24.3) gene have been identified in patients with 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.