Spastic Paraplegia 75
Patient Information
Characteristics
Background and History
This is one of a large number of hereditary neurological disorders that is caused by a specific mutation.
Clinical Correlations
This is an early-onset and progressive neurological disorder. Newborns may have hypotonia (floppiness) due to lack of muscle tone. Neurological development is generally delayed with the result that children are late in achieving milestones. Difficulty walking is common due to spasticity and most individuals never achieve a normal gait. Mental development is also delayed in most individuals and as a result they usually have impaired cognitive abilities with slow learning and, in some cases, mental retardation. The optic nerve does not function normally and as a result vision is decreased. Speech is often slurred. Brain imaging usually reveals underdevelopment of vital brain structures such as the cerebellum.
Genetics
Inheritance
This is an autosomal recessive condition resulting from mutations in both copies of a specific gene. Both parents who have a single copy of the mutation are clinically normal but they can expect that 1 of 4 of their children will inherit both copies and have this disease.
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.
Diagnosis and Prognosis
There are no physical characteristics of this condition in infants and diagnosis may not be possible until childhood. Hypotonia (floppiness) is a nonspecific sign and a feature of numerous neurological disorders. The diagnosis is based on the presence of a constellation of specific neurological signs and symptoms and requires documentation by gene testing. Pediatricians, pediatric neurologists, neuroradiologists, and ophthalmologists are likely to collaborate on the diagnosis.
There is no information on longevity and no treatment results have been reported. Supportive care and physical therapy, speech therapy, special education, and low vision devices may be helpful.
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