Paraplegia familial spastic type 7 (Spastic paraplegia type 7) - Gen SPG7.  

The spastic paraplegia type 7 is part of a group of genetic alterations known as hereditary spastic paraplegia. These changes are characterized by spasticity and development of paraplegia. Hereditary spastic paraplegia the are divided into two types: pure and complex. Pure types involving the lower extremities. Complex types involving the lower extremities and may affect the upper extremities to a lesser degree. Spastic paraplegia complex also affect the structure or function of the brain and peripheral nervous system consists of the nerves that connect the brain and spinal cord to muscles and sensory cells that detect sensation like touch, pain, heat , and sound. The spastic paraplegia type 7 can occur both in pure form and in complex form.

The disease involves spasticity of leg muscles and increased muscle weakness. People with this form of spastic paraplegia may also have hyperreflexia in the arms, dysarthria, dysphagia, nystagmus, mild hearing loss, scoliosis, foot arch elevation, sensory neuropathy, motor neuropathy and amiotrofia. Although the onset of symptoms varies widely among individuals, abnormalities in muscle tone and other characteristics are generally noticeable in adulthood.

This process is due to mutations in the gene SPG7, located on the long arm of chromosome 16 (16q24.3). This gene encodes the protein paraplegin, a member of the family of AAA proteins. This family of proteins plays a role in many cellular activities, including regulation of cellular components and proteins. This protein is one of the proteins that form the complex m-AAA protease, responsible for assembling the ribosomes and removing non - functional proteins in mitochondria.

There are more than 10 mutations in the gene causing the SPG7 spastic paraplegia type 7. Most of these mutations change the amino acids in protein. Mutations in the gene cause malfunction protease m-AAA, causing a buildup of proteins used in the mitochondria of nerve cells, which can result in an increase of cell size, small cell signaling, and alteration in cell movement, leading to the main signs and symptoms of the disease.

This disease is inherited in an autosomal recessive pattern, that is, both copies of the gene in every cell must have mutations for alteration is expressed. The parents of an individual with an autosomal recessive disease have a copy of the mutated gene, but usually show no signs and symptoms of the disease.  

Tests in IVAMI: in IVAMI perform detection of mutations associated with spastic paraplegia type 7, by complete PCR amplification of exons SPG7 gene, and subsequent sequencing.

Samples recommended: EDTA blood collected for separation of blood leukocytes, or impregnated sample card with dried blood (IVAMI may mail the card to deposit the blood sample).