Spastic Paraplegia Type 7

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This entry is adapted from the peer-reviewed paper https://medlineplus.gov/genetics/condition/spastic-paraplegia-type-7

Spastic paraplegia type 7 (also called SPG7) is part of a group of genetic disorders known as hereditary spastic paraplegias.

genetic conditions

1. Introduction

Spastic paraplegia type 7 (also called SPG7) is part of a group of genetic disorders known as hereditary spastic paraplegias. These disorders are characterized by progressive muscle stiffness (spasticity) in the legs and difficulty walking. Hereditary spastic paraplegias are divided into two types: pure and complex. The pure types generally involve only spasticity of the lower limbs and walking difficulties. The complex types involve more widespread problems with the nervous system; the structure or functioning of the brain; and the nerves connecting the brain and spinal cord to muscles and sensory cells that detect sensations such as touch, pain, heat, and sound (the peripheral nervous system). In complex forms, there can also be features outside of the nervous system. Spastic paraplegia type 7 can occur in either the pure or complex form.

Like all hereditary spastic paraplegias, spastic paraplegia type 7 involves spasticity of the leg muscles and some muscle weakness. People with this form of spastic paraplegia can also have ataxia; a pattern of movement abnormalities known as parkinsonism; exaggerated reflexes (hyperreflexia) in the arms; speech difficulties (dysarthria); difficulty swallowing (dysphagia); involuntary movements of the eyes (nystagmus); mild hearing loss; abnormal curvature of the spine (scoliosis); high-arched feet (pes cavus); numbness, tingling, or pain in the arms and legs (sensory neuropathy); disturbance in the nerves used for muscle movement (motor neuropathy); and muscle wasting (amyotrophy). The onset of symptoms varies greatly among those with spastic paraplegia type 7; however, abnormalities in muscle tone and other features usually become noticeable in adulthood.

2. Frequency

The prevalence of all hereditary spastic paraplegias combined is estimated to be 2 to 6 in 100,000 people worldwide. Spastic paraplegia type 7 likely accounts for only a small percentage of all spastic paraplegia cases.

3. Causes

Mutations in the SPG7 gene cause spastic paraplegia type 7. The SPG7 gene provides instructions for producing a protein called paraplegin. Located within the inner membrane of the energy-producing centers of cells (mitochondria), paraplegin is one of the proteins that form a complex called the m-AAA protease. The m-AAA protease acts as an enzyme and is responsible for assembling ribosomes (cellular structures that process the cell's genetic instructions to create proteins) and removing nonfunctional proteins in the mitochondria. When there is a mutation in paraplegin, the m-AAA protease cannot function correctly. Nonfunctional m-AAA proteases cause a build up of unusable proteins in the mitochondria of nerve cells, which can result in swelling of the cell, reduced cell signaling, and impaired cell movement, leading to the major signs and symptoms of spastic paraplegia type 7.

3.1 The gene associated with Spastic paraplegia type 7

SPG7

4. Inheritance

This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but they typically do not show signs and symptoms of the condition.

5. Other Names for This Condition

hereditary spastic paraplegia, paraplegin type
spastic paraplegia 7

References

Atorino L, Silvestri L, Koppen M, Cassina L, Ballabio A, Marconi R, Langer T, Casari G. Loss of m-AAA protease in mitochondria causes complex I deficiency and increased sensitivity to oxidative stress in hereditary spastic paraplegia. JCell Biol. 2003 Nov 24;163(4):777-87.
Coarelli G, Schule R, van de Warrenburg BPC, De Jonghe P, Ewenczyk C,Martinuzzi A, Synofzik M, Hamer EG, Baets J, Anheim M, Schöls L, Deconinck T,Masrori P, Fontaine B, Klockgether T, D'Angelo MG, Monin ML, De Bleecker J,Migeotte I, Charles P, Bassi MT, Klopstock T, Mochel F, Ollagnon-Roman E,D'Hooghe M, Kamm C, Kurzwelly D, Papin M, Davoine CS, Banneau G, Tezenas duMontcel S, Seilhean D, Brice A, Duyckaerts C, Stevanin G, Durr A. Loss ofparaplegin drives spasticity rather than ataxia in a cohort of 241 patients with SPG7. Neurology. 2019 Jun 4;92(23):e2679-e2690. doi:10.1212/WNL.0000000000007606.
Hewamadduma CA, Hoggard N, O'Malley R, Robinson MK, Beauchamp NJ, Segamogaite R, Martindale J, Rodgers T, Rao G, Sarrigiannis P, Shanmugarajah P, Zis P,Sharrack B, McDermott CJ, Shaw PJ, Hadjivassiliou M. Novel genotype-phenotype andMRI correlations in a large cohort of patients with SPG7 mutations. Neurol Genet.2018 Oct 24;4(6):e279. doi: 10.1212/NXG.0000000000000279.Erratum in: Neurol Genet. 2018 Dec 03;4(6):e300.
Patron M, Sprenger HG, Langer T. m-AAA proteases, mitochondrial calciumhomeostasis and neurodegeneration. Cell Res. 2018 Mar;28(3):296-306. doi:10.1038/cr.2018.17.
SPG7 mutations are a common cause of undiagnosed ataxia. Neurology. 2015 May5;84(18):1911. doi: 10.1212/WNL.0000000000001628.
Wilkinson PA, Crosby AH, Turner C, Bradley LJ, Ginsberg L, Wood NW, SchapiraAH, Warner TT. A clinical, genetic and biochemical study of SPG7 mutations inhereditary spastic paraplegia. Brain. 2004 May;127(Pt 5):973-80.

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Subjects: Genetics & Heredity

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Bruce Ren

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Entry Collection: MedlinePlus

Update Date: 23 Dec 2020

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