Understanding Genetics Of Stroke

Stroke is the second leading cause of death and the third leading cause of disability globally. In India, stroke affects approximately 1.8 million people annually, with incidence rising due to aging populations and increasing prevalence of cardiovascular risk factors. While stroke has traditionally been viewed primarily as a vascular disease, genetics plays a significant and increasingly recognized role — both in determining individual risk and in guiding treatment.

Types of Stroke and Their Genetic Basis

Ischaemic Stroke (87% of strokes)

Caused by blockage of a blood vessel supplying the brain. Subtypes include large artery atherosclerosis, cardioembolic stroke (often from atrial fibrillation), small vessel disease, and cryptogenic (unknown cause). Each subtype has distinct genetic contributions.

Haemorrhagic Stroke (13% of strokes)

Caused by rupture of a blood vessel in or around the brain. Includes intracerebral haemorrhage and subarachnoid haemorrhage. Genetic factors influencing blood pressure, coagulation, and vascular integrity are particularly relevant.

Genetic Risk Factors for Stroke

Monogenic Causes

A small proportion of strokes — particularly those occurring in young people — are caused by single-gene mutations:

• CADASIL (NOTCH3 mutations): Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy. Causes recurrent strokes and dementia, typically presenting in the 40s–50s.
• Fabry disease (GLA mutations): X-linked lysosomal storage disorder causing stroke, kidney disease, and heart disease. Treatable with enzyme replacement therapy.
• Sickle cell disease (HBB mutations): Causes stroke through multiple mechanisms; children with sickle cell disease have a 300× higher stroke risk than the general population.
• Factor V Leiden and Prothrombin G20210A: Common thrombophilia mutations that increase clotting risk and stroke risk, particularly in younger patients.

Polygenic Risk

Common stroke has significant polygenic heritability. Genome-wide association studies have identified over 30 genetic loci associated with stroke risk, many overlapping with cardiovascular disease risk loci. Key genetic risk factors include variants influencing blood pressure, atrial fibrillation susceptibility, lipid levels, and coagulation.

Pharmacogenomics in Stroke Treatment and Prevention

Genetics influences both stroke treatment and secondary prevention. CYP2C19 variants affect clopidogrel activation — poor metabolizers have reduced antiplatelet effect and higher recurrent stroke risk. Warfarin dosing for stroke prevention in atrial fibrillation is influenced by CYP2C9 and VKORC1 variants. Understanding these pharmacogenomic factors allows for more effective secondary stroke prevention.

FAQs

Should I get genetic testing if I've had a stroke?

Genetic testing is particularly valuable for young stroke patients (under 55), those with a family history of stroke, and those with recurrent strokes despite standard treatment. Testing can identify monogenic causes that require specific treatment and pharmacogenomic variants that affect secondary prevention medications.

Can genetic testing predict stroke risk?

Genetic testing can identify inherited risk factors for stroke — including thrombophilia mutations, CADASIL, Fabry disease, and polygenic risk. This information allows for targeted prevention strategies in high-risk individuals.