Genetic Causes of Stroke
5 sections · 25 min
Recognizing Genetic Stroke: Red Flags and Epidemiology
Approximately 5–10% of all strokes and up to 25–30% of strokes in patients under 45 years have a definable genetic cause. Genetic stroke syndromes should be suspected when stroke occurs in young patients, is recurrent, affects multiple family members, is associated with specific non-stroke neurological features, or has characteristic MRI findings. A systematic approach to genetic diagnosis has direct therapeutic implications and informs family member screening.
Key Points
- Red flags for genetic stroke: age <45 years without traditional cardiovascular risk factors, family history of early stroke, recurrent strokes in multiple vascular territories, stroke with concurrent white matter disease, stroke with systemic features (rash, renal disease, ophthalmological findings), stroke with hearing loss or migraine
- Monogenic vs. polygenic contribution: most common stroke is multifactorial; rare monogenic causes include CADASIL, MELAS, CARASIL, COL4A1/2 angiopathy, Fabry disease, sickle cell disease, coagulopathies, FMD
- Children with stroke: cardiac embolism, sickle cell disease, arterial dissection, CNS vasculitis, and metabolic disorders (homocystinuria, organic acidemias) are important causes; prothrombotic workup and echo essential
- MRI red flags: cortical/parieto-occipital signal abnormality crossing vascular territories (MELAS stroke-like episodes), periventricular white matter disease in young adult (CADASIL), cortical restricted diffusion in non-vascular distribution (MELAS in acute phase), temporal lobe WMH (CADASIL), cerebellar strokes in young adults (COL4A1)
- Genomic testing yield in young stroke: comprehensive stroke genetics panel or exome sequencing has a diagnostic yield of ~15–20% in young cryptogenic stroke patients at specialized centers
✦ Check Your Understanding
MTHFR C677T homozygosity is found on a thrombophilia panel ordered during young stroke workup. The appropriate clinical response is:
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CADASIL: Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy
CADASIL is the most common hereditary stroke disorder in adults, caused by autosomal dominant pathogenic variants in NOTCH3 — specifically stereotyped cysteine-altering variants in the epidermal growth factor-like repeat (EGF-r) domain of the extracellular domain, causing protein aggregation in the walls of small arteries throughout the body. It is a primary arteriopathy — not a coagulopathy — affecting cerebral small vessels.
Key Points
- NOTCH3: all pathogenic CADASIL variants are cysteine-altering variants in the EGF-r domain (exons 2–24); they cause an odd number of cysteines in the domain, leading to aberrant disulfide bonding and GOM (granular osmiophilic material) deposits in vessel walls
- Clinical tetrad: migraine with aura (often first symptom, 3rd–4th decade), recurrent subcortical lacunar strokes (4th–5th decade), psychiatric disturbance (depression, apathy, personality change), progressive cognitive decline → vascular dementia (5th–6th decade)
- MRI signature: extensive periventricular and subcortical white matter hyperintensities; early involvement of anterior temporal lobes and external capsule is characteristic and relatively specific; multiple old lacunar infarcts in basal ganglia, thalamus, pons
- Diagnosis: NOTCH3 sequencing (targeted EGF-r domain exons or whole gene); skin biopsy electron microscopy showing GOM deposits (supportive but less sensitive than sequencing); GOM on biopsy is not specific to EGF-r cysteine variants
- No disease-modifying therapy; antiplatelet therapy (aspirin) for secondary stroke prevention; statins, antihypertensives as for other small vessel disease; anticoagulation is not beneficial; migraine management — avoid triptans in active infarct history
✦ Check Your Understanding
A 38-year-old woman presents with a third episode of subcortical lacunar stroke. She has a history of migraine with aura since age 28 and her father had dementia and strokes in his 50s. MRI shows extensive periventricular white matter changes and old lacunar infarcts in the external capsule and anterior temporal lobes. The most likely diagnosis is:
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MELAS and Mitochondrial Stroke-Like Episodes
Stroke-like episodes (SLEs) in MELAS differ fundamentally from ischemic stroke: they are caused by focal neuronal energy failure, not vascular occlusion. This distinction has critical management implications — thrombolytics are contraindicated. MELAS is most commonly caused by the m.3243A>G variant in MT-TL1 with maternal inheritance and variable heteroplasmy. For comprehensive coverage of MELAS and mitochondrial disorders, see the Mitochondrial Disorders module.
Key Points
- m.3243A>G (MT-TL1): ~80% of MELAS; maternal inheritance; blood heteroplasmy underestimates severity — muscle biopsy or urinary sediment preferred for testing
- Key stroke distinction: SLEs are NOT vascular occlusion — thrombolytics are contraindicated and could cause hemorrhage; mechanism is focal mitochondrial dysfunction causing cytotoxic and vasogenic edema in non-vascular distributions
- MRI differentiation from ischemic stroke: DWI cortical signal crossing vascular boundaries (often occipital/parietal); basal ganglia calcification; lactate peak on MRS; signal evolves over days-weeks unlike acute infarct
- Clinical clues suggesting MELAS over ischemic stroke: young patient, cortical blindness or hemianopia, seizures, hearing loss, diabetes, short stature, elevated serum lactate, family history of maternal inheritance pattern
- Stroke-specific management: IV L-arginine during acute SLE (nitric oxide precursor); seizure control (avoid valproate — inhibits complex I); avoid metformin (worsens lactic acidosis); CoQ10, riboflavin, L-carnitine as supportive therapy
✦ Check Your Understanding
A 16-year-old presents with sudden onset cortical blindness. MRI DWI shows restricted diffusion in the bilateral occipital cortex crossing vascular territories. Lactate is 4.2 mmol/L. The acute management should include:
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Hereditary Coagulopathies and Vasculopathies
Several hereditary conditions affecting coagulation or vascular wall structure predispose to ischemic stroke or intracranial hemorrhage. These conditions require specific genetic testing and targeted management distinct from the general approach to stroke secondary prevention.
Key Points
- Factor V Leiden (F5 c.1601G>A, p.Arg506Gln): most common inherited thrombophilia (5% European prevalence); APC resistance; venous thromboembolic disease > arterial; modest stroke risk increase, predominantly venous sinus thrombosis; heterozygotes rarely need anticoagulation without additional risk factors
- Prothrombin G20210A (F2): second most common thrombophilia (~2% Europeans); venous > arterial; combined factor V Leiden + prothrombin mutation substantially increases VTE risk
- MTHFR C677T: associated with elevated homocysteine (modest); NOT an independent stroke risk factor when homocysteine is normal; testing not recommended for stroke workup — measure homocysteine level directly instead
- COL4A1/COL4A2 mutations: autosomal dominant; cause of hereditary porencephaly, small vessel disease, and intracerebral hemorrhage; MRI shows periventricular WMH and microbleeds; also associated with renal disease (HANAC syndrome for COL4A1)
- Fabry disease (GLA gene, X-linked): alpha-galactosidase A deficiency; stroke in young adults (3rd–4th decade) due to small vessel lipid deposition; acroparesthesias, angiokeratomas, corneal opacity, renal disease; enzyme replacement therapy (agalsidase) is available — genetic diagnosis has direct treatment implications
✦ Check Your Understanding
A 32-year-old man with acroparesthesias, renal insufficiency, and no traditional stroke risk factors presents with a lacunar infarct. His maternal uncle had early renal failure and a stroke at 40. The most appropriate screening test is:
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Genetic Workup and Secondary Prevention in Young Stroke
A systematic, stepwise approach to genetic evaluation in young stroke patients maximizes diagnostic yield while remaining cost-effective. The workup is guided by clinical phenotype, stroke mechanism (ischemic vs. hemorrhagic, large vessel vs. small vessel vs. cardioembolic), and family history. Genetic diagnosis has implications for treatment, secondary prevention, and family screening.
Key Points
- First-tier workup: standard stroke workup (MRI, echo, ECG, Holter, carotid/vertebral imaging) to exclude cardioembolic and atherosclerotic causes; CBC, BMP, LFTs, ESR/CRP; homocysteine, lipids; hemoglobin electrophoresis in appropriate populations
- Second-tier targeted testing: lactate/pyruvate and CSF lactate (MELAS); coagulation studies and thrombophilia panel (factor V Leiden, prothrombin G20210A, antithrombin, protein C, protein S — note: acute stroke and anticoagulation affect protein C/S levels); skin/blood NOTCH3 if clinical/MRI features suggest CADASIL
- Third-tier comprehensive genetic testing: alpha-galactosidase A activity (males)/GLA sequencing (Fabry disease); mitochondrial DNA sequencing/NGS; COL4A1/2 sequencing; stroke gene panel or exome for cryptogenic young stroke
- Sickle cell disease screening: hemoglobin electrophoresis; TCD (transcranial Doppler) screening in children with SCD; chronic transfusion therapy reduces stroke risk in SCD children with elevated TCD velocities (>200 cm/s)
- Secondary prevention by mechanism: antiplatelet for small vessel and large artery atherosclerosis; anticoagulation for cardioembolic and coagulopathy-related; enzyme replacement for Fabry; arginine supplementation for MELAS; avoid oral contraceptives in women with thrombophilia or CADASIL
✦ Check Your Understanding
A 7-year-old child with sickle cell disease (HbSS) has transcranial Doppler velocities of 220 cm/s in the right MCA. The evidence-based intervention that most reduces stroke risk is:
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