Predominant cerebellar phenotype in spastic paraplegia 7 (SPG7)

Movement disorders in hereditary spastic paraplegias

BACKGROUND

 Hereditary or familial spastic paraplegias (SPG) comprise a group of genetically and phenotypically heterogeneous diseases characterized by progressive degeneration of the corticospinal tracts. The complicated forms evolve with other various neurological signs and symptoms, including movement disorders and ataxia.

OBJECTIVE

 To summarize the clinical descriptions of SPG that manifest with movement disorders or ataxias to assist the clinician in the task of diagnosing these diseases.

METHODS

 We conducted a narrative review of the literature, including case reports, case series, review articles and observational studies published in English until December 2022.

RESULTS

 Juvenile or early-onset parkinsonism with variable levodopa-responsiveness have been reported, mainly in SPG7 and SPG11. Dystonia can be observed in patients with SPG7, SPG11, SPG22, SPG26, SPG35, SPG48, SPG49, SPG58, SPG64 and SPG76. Tremor is not a frequent finding in patients with SPG, but it is described in different types of SPG, including SPG7, SPG9, SPG11, SPG15, and SPG76. Myoclonus is rarely described in SPG, affecting patients with SPG4, SPG7, SPG35, SPG48, and SPOAN (spastic paraplegia, optic atrophy, and neuropathy). SPG4, SPG6, SPG10, SPG27, SPG30 and SPG31 may rarely present with ataxia with cerebellar atrophy. And autosomal recessive SPG such as SPG7 and SPG11 can also present with ataxia.

CONCLUSION

 Patients with SPG may present with different forms of movement disorders such as parkinsonism, dystonia, tremor, myoclonus and ataxia. The specific movement disorder in the clinical manifestation of a patient with SPG may be a clinical clue for the diagnosis.

Phenotypic and Genetic Heterogeneity of Adult Patients with Hereditary Spastic Paraplegia from Serbia

Hereditary spastic paraplegia (HSP) is among the most genetically diverse of all monogenic diseases. The aim was to analyze the genetic causes of HSP among adult Serbian patients. The study comprised 74 patients from 65 families clinically diagnosed with HSP during a nine-year prospective period. A panel of thirteen genes was analyzed: L1CAM (SPG1), PLP1 (SPG2), ATL1 (SPG3A), SPAST (SPG4), CYP7B1 (SPG5A), SPG7 (SPG7), KIF5A (SPG10), SPG11 (SPG11), ZYFVE26 (SPG15), REEP1 (SPG31), ATP13A2 (SPG78), DYNC1H1, and BICD2 using a next generation sequencing-based technique. A copy number variation (CNV) test for SPAST, SPG7, and SPG11 was also performed. Twenty-three patients from 19 families (29.2%) had conclusive genetic findings, including 75.0% of families with autosomal dominant and 25.0% with autosomal recessive inheritance, and 15.7% of sporadic cases. Twelve families had mutations in the SPAST gene, usually with a pure HSP phenotype. Three sporadic patients had conclusive findings in the SPG11 gene. Two unrelated patients carried a homozygous pathogenic mutation c.233T>A (p.L78*) in SPG7 that is a founder Roma mutation. One patient had a heterozygous de novo variant in the KIF5A gene, and one had a compound heterozygous mutation in the ZYFVE26 gene. The combined genetic yield of our gene panel and CNV analysis for HSP was around 30%. Our findings broaden the knowledge on the genetic epidemiology of HSP, with implications for molecular diagnostics in this region.

Hereditary spastic paraplegia: new insights into clinical variability and spasticity-ataxia phenotype, and novel mutations

INTRODUCTION

Hereditary spastic paraplegias (HSPs), a genetically heterogeneous group of neurodegenerative diseases, have an incidence of around 3 to 9 individuals every 100,000. Due to the broad clinical and genetic variability of HSPs, it is challenging to diagnose the disorder quickly and precisely. Hereditary spastic ataxias (HSAs) and HSPs are overlapping diseases, and their intersection has been gradually identified by next-generation sequencing. The idea of the spasticity-ataxia phenotype (SAP) spectrum is further substantiated by the similarities in phenotypes and underlying genes in ataxias and inherited spastic paraplegias and the related cellular processes and disease mechanisms these disorders exhibit.

METHODS

Whole-exome sequencing was performed on the 25 spastic or spastic-ataxic gait patients.

RESULTS

Twenty-two specific HSPs-HSAs-SAP mutations, including 14 novel mutations, were found in 25 cases from 18 Turkish and 2 Syrian families. This research discovers many novel hereditary spastic paraplegia (HSP) mutations and shows a robust genotype-phenotype heterogeneity in the disease.

CONCLUSIONS

This research helped expand the clinical and molecular scope of HSP and clarified the concept of the spasticity-ataxia phenotype, further enhancing our understanding of the complicated form of HSP and its association with ataxia. Our data broadens the spectrum of HSPs and HSAs related gene mutations and provides insights for genotype-phenotype correlations for HSPs and HSAs.

[Common forms of hereditary spastic paraplegias]

A group of hereditary spastic paraplegias includes about 80 spastic paraplegia genes (SPG): forms with identified (almost 70) or only mapped (about 10) genes. Methods of next generation sequencing (NGS), along with new SPG discovering, modify knowledge about earlier delineated SPG. Clinical and genetic characteristics of common autosomal dominant (SPG4, SPG3, SPG31) and autosomal recessive (SPG11, SPG7, SPG15) forms are presented.