SNP Shot: Genomic Insights

Spastic paraplegia type 7 (SPG7) is a type of hereditary spastic paraplegia, a group of over 80 genetic disorders. These disorders primarily affect the central nervous system (brain and spinal cord), particularly the neurons that extend down the spinal cord. These neurons control muscle movement and sensation. The main symptoms of hereditary spastic paraplegias include increasing stiffness (spasticity) in the legs and difficulty walking.

Hereditary spastic paraplegias are classified as either pure or complex. Pure forms mainly involve spasticity and walking problems in the lower limbs. Complex forms affect the nervous system more broadly, potentially involving brain structure or function, and the peripheral nervous system (nerves connecting the brain and spinal cord to muscles and sensory cells). Complex forms can also have features outside of the nervous system. Spastic paraplegia type 7 can manifest as either the pure or complex type.

Like other hereditary spastic paraplegias, spastic paraplegia type 7 is characterized by leg muscle spasticity and some muscle weakness. Individuals with this condition may also experience ataxia, parkinsonism, hyperreflexia in the arms, dysarthria, dysphagia, nystagmus, mild hearing loss, scoliosis, pes cavus, sensory neuropathy, motor neuropathy, and amyotrophy. The age when symptoms appear varies significantly among individuals with spastic paraplegia type 7, but muscle tone abnormalities and other features typically become apparent in adulthood.

Inheritance:

Spastic paraplegia type 7 is usually inherited in an autosomal recessive pattern. This means that both copies of the SPG7 gene in each cell must have mutations for the condition to develop. In autosomal recessive inheritance, each parent carries one copy of the mutated gene but usually doesn't show symptoms of the condition. Rarely, spastic paraplegia type 7 is inherited in an autosomal dominant pattern, where only one copy of the altered gene is sufficient to cause the disorder.