Hereditary Spastic Paraplegia in Alberta: Lessons from a Well-Defined Cohort Including the Indigenous Population.

Background: Hereditary spastic paraplegias (HSP) are rare disorders sharing common features of leg spasticity with gait impairment. Simple and complex forms are recognized; over 50% of cases remain unsolved genetically. Little is known about the genetics of HSP among Indigenous Peoples.

Objectives: To describe clinical, radiological, and genetic features of HSP in Alberta, Canada, and evaluate genetic variability among ethnic groups.

Methods: Patients with HSP were recruited between 2012 and 2021, and enrolled in an observational study. Genetic testing through research and/or clinical laboratories was performed.

Results: 100 patients from 86 Albertan families were enrolled. Overall prevalence was 2.3 per 100,000, with 2.8 per 100,000 in the Indigenous population. Forty-eight families (56%) were found to have pathogenic variants in 17 genes, including SPAST (29.2%), SPG7 (20.8%), SPG11 (8.3%), CAPN1 (6.3%), and SACS (6.3%). 58% of families had complex HSP. 36/66 White (European) families, 5/8 Indigenous families, 4/8 Asian families and 2/3 Middle Eastern families were confirmed with a genetic diagnosis. One Black (African) family was enrolled and tested positive for PI4KA. In Indigenous families, pathogenic variants were found in CTNNB1, SACS, SPG7, and SYNE1. Abnormalities of brain MRI were more frequently observed in patients with SACS, SPG7, SPG11, and ANO10.

Conclusions: This study details findings in HSP patients in Alberta and is the first study to examine prevalence and types of HSP in the Indigenous Peoples of Alberta. It highlights the need for familiarity with the phenotypes and genotypes in the different ethnic populations in Alberta.