DEFINITION
Hereditary Spastic Paraplegia is a group of inherited diseases whose main feature is progressive stiffness and contraction (spasticity) in the lower limbs, as a result of damage to or dysfunction of the nerves.
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Hereditary Spastic Paraplegia
EPIDEMIOLOGY
Worldwide, the prevalence of all hereditary spastic paraplegias combined is estimated to be 2 to 6 in 100,000 people
SYMPTOMS
progressive stiffness and contraction (spasticity) in the lower limbs
DIAGNOSIS
histopathology
radiology
NMR
laboratory tests
Autosomal dominant spastic paraplegias: a review of 89 families resulting from a portuguese survey. 2013
- IMPORTANCE:
Hereditary spastic paraplegias (HSPs) are a group of diseases caused by corticospinal tract degeneration. Mutations in 3 genes (SPG4, SPG3, and SPG31) are said to be the cause in half of the autosomal dominant HSPs (AD-HSPs). This study is a systematic review of families with HSP resulting from a population-based survey. Novel genotype-phenotype correlations were established.
OBJECTIVE:
To describe the clinical, genetic, and epidemiological features of Portuguese AD-HSP families.
DESIGN:
Retrospective medical record review.
SETTING:
A population-based systematic survey of hereditary ataxias and spastic paraplegias conducted in Portugal from 1993 to 2004.
PARTICIPANTS:
Families with AD-HSP.
MAIN OUTCOME MEASURE:
Mutation detection in the most prevalent genes.
RESULTS:
We identified 239 patients belonging to 89 AD-HSP families. The prevalence was 2.4 in 100 000. Thirty-one distinct mutations (26 in SPG4, 4 in SPG3, and 1 in SPG31) segregated in 41% of the families (33.7%, 6.2%, and 1.2% had SPG4, SPG3 and SPG31 mutations, respectively). Seven of the SPG4 mutations were novel, and 7% of all SPG4 mutations were deletions. When disease onset was before the first decade, 31% had SPG4 mutations and 27% had SPG3 mutations. In patients with SPG4 mutations, those with large deletions had the earliest disease onset, followed by those with missense, frameshift, nonsense, and alternative-splicing mutations. Rate of disease progression was not significantly different among patients with SPG3 and SPG4 mutations in a multivariate analysis. For patients with SPG4 mutations, disease progression was worst in patients with later-onset disease.
CONCLUSIONS AND RELEVANCE:
The prevalence of AD-HSP and frequency of SPG3 and SPG4 mutations in the current study were similar to what has been described in other studies except that the frequency of SPG4 deletions was lower. In contrast, the frequency of SPG31 mutations in the current study was rare compared with other studies. The most interesting aspects of this study are that even in patients with early-onset disease the probability of finding a SPG4 mutation was higher than for patients with SPG3 mutations; there was no difference in disease progression with genotype but an association with the age at onset; 7 new SPG4 mutations were identified; and for the first time, to our knowledge, the nature of the SPG4 mutations was found to predict the age at onset.
SPG4
PATHOGENESIS
Receptor expression-enhancing proteins (REEPs; Yop1p in yeast) and Reticulon proteins form large oligomers, referred to here as morphogen complexes, to shape the tubular endoplasmic reticulum (ER) network. Atlastin proteins (Sey1p in yeast) interact with REEPs and Reticulons and are enriched in puncta along the tubules (shown by yellow circles), including at three-way junctions. A blown-out image of the axon shows a tubular ER three-way junction. A nested blown-out image of a presumptive ER morphogen complex depicts the proposed membrane topologies for proteins involved in generating curvature of ER tubules, as well as mediating microtubule interactions and fusion of ER tubules. AAA, ATPases associated with diverse cellular activities (AAA) ATPase domain; GTP, Atlastin GTPase domain; MIT, microtubule-interacting and trafficking protein domain; MBD, microtubule-binding domain; REEP, receptor expression-enhancing protein; Rtn, reticulon. (Hereditary spastic paraplegias: membrane traffic and the motor pathway, 2011) (more details..)
PATIENT RISK FACTORS
Vascular
Genetic
Acquired
Hormonal
Genetic
Acquired
TISSUE SPECIFIC RISK FACTORS
anatomical (due its structure)
vascular (due to the local circulation)
physiopathological (due to tissue function and activity)
COMPLICATIONS
THERAPY
