HOMOZYGOUS FAMILIAL HYPERCHOLESTEROLEMIA IN CANADA

Homozygous familial hypercholesterolemia (HoFH) is an orphan disease characterized by extremely high levels of plasma levels of LDL-C. Affected patients develop clinical atherosclerotic cardiovascular disease (ASCVD) in youth and survival > 30 years of age was unusual until the advent of medications (statins) and extracorporeal LDL filtration (apheresis) techniques. HoFH is an autosomal co-dominant condition defined as an LDL-C > 13 mmol/L in adults without treatment and homozygous or compound heterozygous mutations of the LDLR gene. HoFH has a genetic probability of ∼1/386,000 and the rare diseases inventory Orphanet estimates its worldwide prevalence at 1/1,000,000 individuals. Canada is known to have several regions with a founder effect for HoFH and we identified 79 cases across the country. Data from other countries show a median survival of HoFH patients at <40 years of age. Clinical outcomes in HoFH patients, especially ASCVD events (fatal and non-fatal myocardial infarctions, strokes and peripheral vascular disease) and severe calcific aortic stenosis, are difficult to capture, in part because of the rarity of the disorder and the lack of registry focusing on this disease. The objective of our project is to obtain a comprehensive registry of HoFH in Canada, estimate the cost to society caused by HoFH burden of disease in Canada, and implement changes to advocate access to specialized care for these patients.

Here, we present preliminary data (Table 1) on our Canadian HoFH registry, including medical history, levels of LDL-C, treatments and outcomes of 21 HoFH patients.

We plan to use this data at provincial and national levels, in help with the Canadian Organization for Rare Diseases (CORD) and the Réseau Québecois des maladies orphelines (RQMO), to provide HoFH patients access to care, including PCSK9 inhibitors, orphan drugs such as lomitapide and evinacumab, and treatment techniques such as extracorporeal LDL filtration (apheresis). This work will provide important new health-related knowledge about the determinants of ASCVD risk and phenotypic manifestations of HoFH in Canada and examine the quality of life and burden to the healthcare system.