OMIM ID:
Spastic Paraplegia, Optic Atrophy, and Neuropathy
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Non-progressive optic atrophy with vision loss is described as congenital in onset.
Systemic Features
Progressive spasticity has its onset in infancy with loss of independent mobility usually in the second decade of life. An exaggerated startle response occurs in some individuals. All patients are confined to wheelchairs after 15 years of age due to progressive motor neuropathy. No intellectual disability has been reported. Joint contractures occur. Dysarthria is notable in the third decade of life. Eventually joint contractures and spine deformities occur.
Genetics
Inheritance
Homozygous mutations in the KLC2 gene (11q13.2) have been found in this disorder. A homozygous 216-bp deletion in a non-coding region upstream of the gene results in overexpression of the gene not found in heterozygotes.
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.