Monogenic Stroke Syndromes

While most strokes result from the interaction of multiple genes with lifestyle and environmental factors, several monogenic disorders present with stroke as a major clinical feature. Although individually rare, recognition of these syndromes is critical — a molecular diagnosis provides prognostic information, prevents unnecessary testing, guides family counseling, and in some cases enables specific treatment.

When to Suspect a Monogenic Stroke Syndrome

Monogenic Cerebral Small Vessel Diseases

CADASIL

Cerebral Autosomal Dominant Arteriopathy with Subcortical Infarcts and Leukoencephalopathy

• Genetics: AD; NOTCH3 (19p13); mutations alter cysteine residues in EGF-like repeats
  • Earlier stroke onset with mutations in EGFr domains 1–6 than 7–34
• Pathology: Granular osmiophilic material (GOM) in vessel walls; smooth muscle cell degeneration
• Clinical features:
  • Migraine with aura (40% inaugural; onset ~30 years)
  • Lacunar strokes (onset 40–60 years) → mute bedridden state in ~10 years
  • Progressive cognitive decline → subcortical dementia
  • Mood disturbances (20–30%), acute encephalopathy
  • Suspect in: unexplained symmetric periventricular WMH + family history of migraine, stroke, mood disorder, or dementia
• Imaging:
  • Anterior temporal pole WMH (90%) + external capsule involvement — highly specific
  • Confluent WMH; lacunes; microbleeds (30%)
  • MRI changes precede symptoms (appear by age 20–35)
• Diagnosis: Genetic testing is gold standard; if variant of unknown significance → skin biopsy for GOM or NOTCH3 immunostaining
• Management:
  • Antiplatelets: No evidence for primary or secondary prevention (commonly used)
  • Statins: No evidence to support use
  • Anticoagulants: Not recommended, but not contraindicated if other indication (e.g., AF)
  • Triptans: No evidence to contraindicate
  • Oral contraceptives: No evidence to contraindicate
  • Anesthesia: Maintain strict hemodynamic stability (impaired cerebral autoregulation)
  • Pregnancy: Not contraindicated; no prophylactic ASA/heparin needed; transient neurological events common during labor (migraine-like)
  • Risk factor control: Smoking cessation, BP control (Class 1, LOE C-LD)

CARASIL

Cerebral Autosomal Recessive Arteriopathy with Subcortical Infarcts and Leukoencephalopathy

• Genetics: AR; biallelic HTRA1 mutations (homozygous or compound heterozygous); mainly reported in Japanese/Chinese populations
• Pathology: Arteriosclerosis, loss of vascular smooth muscle, hyalinization — NO GOM (unlike CADASIL)
• Clinical features:
  • Triad: Premature alopecia (90%, by age 20) + spondylosis/disc herniation (2nd–3rd decade) + lacunar strokes
  • First stroke at 30–40 years; bedridden in ~10 years
  • Early vascular dementia, gait impairment, pseudobulbar palsy
  • Seizures, psychiatric disturbances
  • Normotensive
• Imaging: WMH starting by age 20; may involve anterior temporal lobes; lacunes
• Diagnosis: HTRA1 genetic testing; clinical triad is highly suggestive
• Management: Supportive; no evidence for antiplatelets

HTRA1-Related Autosomal Dominant Disease

• Genetics: AD; heterozygous HTRA1 mutations (distinct from CARASIL)
• Clinical features:
  • Later onset and milder than CARASIL (stroke onset ~60 years)
  • Lacunar strokes, cognitive impairment, encephalopathy
  • Less frequent alopecia and spondylosis
• Pathology: Diffuse myelin pallor sparing U-fibers (resembles CADASIL)
• Diagnosis: Not all mutations are pathogenic — enzyme activity testing may be needed

CARASAL

Cathepsin A-Related Arteriopathy with Strokes and Leukoencephalopathy

• Genetics: AD; CTSA gene mutation (encodes cathepsin-A carboxypeptidase)
• Clinical features:
  • Very rare (~19 cases reported)
  • Ischemic or hemorrhagic strokes, cognitive impairment, migraine
  • Dystonia is pathognomonic (but rare)
  • Some patients asymptomatic despite extensive WMH
• Imaging: Leukoencephalopathy involving brainstem, cerebellar peduncles, subcortical WM (sparing U-fibers)
• Management: No specific treatment

Fabry Disease

• Genetics: X-linked; GLA gene (Xq22); affects 1 in 40,000; females can be symptomatic
• Pathology: α-galactosidase A deficiency → accumulation of Gb3 in vessels, neurons, multiple organs
• Clinical features:
  • Classic form (childhood): Burning pain in hands/feet triggered by stress/exercise/fever, hypohidrosis, angiokeratomas (lower abdomen, upper thighs — "bathing suit distribution"), GI symptoms
  • Late-onset form: Isolated organ involvement without classic features
  • Stroke: Age 20–50; usually ischemic (posterior circulation predominant); hemorrhagic and CVT can occur
  • Fabry accounts for ~1% of cryptogenic strokes
  • Cardiomyopathy, arrhythmias, progressive renal failure
  • Cornea verticillata
• Imaging: WMH (50%); pulvinar sign (T1 hyperintensity); basilar dolichoectasia
• Diagnosis:
  • Males: Blood α-galactosidase A level first → if low, confirm with genetics
  • Females: Genetic testing first (enzyme often normal)
• Management:
  • Enzyme replacement therapy (agalsidase beta) or chaperone therapy (migalastat for specific variants)
  • Early diagnosis critical for effective treatment
  • tPA: Not contraindicated
  • Antiplatelets: No evidence for primary prevention; use for secondary prevention
  • Neuropsychological testing recommended

COL4A1/COL4A2-Related Disorders

• Genetics: AD; COL4A1/COL4A2 (13q34); type IV collagen makes basement membrane of all vessels
• Pathology: Defective basement membrane → vessel wall fragility
• Clinical features:
  • Children: ICH, porencephaly, schizencephaly, intracranial aneurysms
  • Adults: Hemorrhagic > ischemic strokes (onset 30s–40s); ICH often related to trauma, physical activity, or anticoagulation
  • HANAC syndrome: Hereditary Angiopathy, Nephropathy, Aneurysms, Muscle Cramps
  • Retinal vessel tortuosity, hemorrhages, early cataracts
  • Hematuria, renal/hepatic cysts
• Suspect when:
  • Deep ICH of undetermined etiology
  • WMH of undetermined etiology
  • FHx of cerebral hemorrhage, porencephaly, retinal vessel tortuosity, hematuria, early cataracts, aneurysms
• Imaging: ICH, microbleeds, WMH, lacunes — usually subcortical location
• Workup: MRI brain, CTA head/neck (aneurysms), TTE, retinal exam, CK levels, urinalysis
• Management:
  • Antiplatelets and anticoagulants: NOT recommended
  • tPA: NOT recommended
  • Avoid contact sports/high brain trauma risk activities
  • Cesarean section should be considered for mothers delivering affected fetus
  • Pre-symptomatic testing of family members

PADMAL

Pontine Autosomal Dominant Microangiopathy and Leukoencephalopathy

• Genetics: AD; COL4A1 mutation in 3' untranslated region → upregulated expression
• Clinical features: Adult-onset pontine infarcts; early death

RVCL-S

Retinal Vasculopathy with Cerebral Leukodystrophy and Systemic Manifestations

• Genetics: AD; TREX1 gene frameshift mutation → mis-localization of DNA exonuclease
• Clinical features:
  • Very rare; onset 4th–5th decade; death within 5–10 years
  • Retina: Progressive vasculopathy (capillary dropout, neovascularization)
  • Brain: Cognitive impairment, focal deficits, migraines, seizures
  • Systemic: Kidney/liver failure, Raynaud's, GI bleeding, thyroid disease
• Imaging:
  • Punctate T2 hyperintensities OR large enhancing lesions mimicking tumors/tumefactive inflammation ("pseudotumors")
  • CT: WM calcifications in 50%
  • Does NOT cause lacunar strokes
• Management: No evidence for antiplatelets or immunosuppression; intravitreal bevacizumab for retinal neovascularization

Mitochondrial Disease

MELAS

Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like Episodes

• Genetics: Maternal inheritance (mtDNA, usually m.3243A>G) or AR (POLG mutations); prevalence ~1:5,000–1:6,000
• Clinical features:
  • Stroke-like episodes (SLEs): Subacute syndrome with headache, nausea, vomiting, encephalopathy, focal deficits, seizures
  • Onset typically before age 40 (late onset recognized)
  • Sensorineural hearing loss (nearly universal)
  • Short stature, ptosis, myopathy, exercise intolerance
  • Diabetes mellitus, cardiomyopathy, arrhythmias
  • Psychiatric manifestations common
• Imaging:
  • Lesions affect cortex and juxtacortical WM, NOT following vascular territories
  • Predominantly posterior (temporal, parietal, occipital)
  • Lesions may resolve or progress to cortical laminar necrosis
  • MR spectroscopy: Elevated lactate peak
• Diagnosis:
  • Elevated serum/CSF lactate (CSF more sensitive)
  • Test m.3243A>G mutation in urine (blood may miss it); if negative → POLG sequencing; if negative → muscle biopsy
  • Muscle biopsy: Ragged red fibers, strongly SDH-positive
• Management:
  • tPA: NOT indicated for stroke-like episodes
  • Antiplatelets: NOT indicated for secondary prevention
  • L-arginine: No evidence to support use
  • Steroids: No evidence to support, but not contraindicated
  • Seizures: Treat aggressively with levetiracetam, lacosamide, or benzodiazepines
  • Avoid: Valproate (especially with POLG mutations), aminoglycosides
  • Monitor for arrhythmias (telemetry during SLEs, especially if using antipsychotics)
  • "Mitochondrial cocktail" (CoQ10, L-carnitine, B vitamins): Limited evidence

Connective Tissue Disorders

Ehlers-Danlos Syndrome Type IV (Vascular Type)

• Genetics: Autosomal dominant; COL3A1 gene (2q31); abnormal type III collagen
• Pathology: Defective collagen in vessel walls → arterial fragility, dissection, rupture
• Clinical features:
  • Thin, translucent skin with visible veins
  • Easy bruising, acrogeria (aged-appearing hands/feet)
  • Spontaneous arterial dissection or rupture (carotid, vertebral, aorta)
  • Intracranial aneurysms (~10% prevalence)
  • Organ rupture (colon, uterus)
  • Death typically by age 40–50 from vascular complications
• Imaging: CTA/MRA for dissection; conventional angiography relatively contraindicated (risk of vessel injury)
• Diagnosis: Clinical; genetic testing; skin biopsy (collagen studies)
• Treatment: Avoid invasive procedures when possible; blood pressure control; celiprolol may reduce vascular events; genetic counseling

Marfan Syndrome

• Genetics: Autosomal dominant; FBN1 gene (15q21); defective fibrillin-1
• Pathology: Connective tissue weakness affecting aorta, heart valves, eyes, skeleton
• Clinical features:
  • Tall stature, arachnodactyly, pectus deformities, scoliosis
  • Lens dislocation (ectopia lentis), myopia
  • Aortic root dilatation, dissection, MVP
  • Cervical artery dissection (carotid, vertebral)
  • Intracranial aneurysms
  • Dural ectasia
• Diagnosis: Revised Ghent criteria (clinical + genetic); echocardiography for aortic root
• Treatment: Beta-blockers or ARBs for aortic dilatation; prophylactic aortic surgery when indicated; avoid contact sports

Pseudoxanthoma Elasticum (PXE)

• Genetics: Autosomal recessive (most common); ABCC6 gene (16p13); encodes transmembrane transporter
• Pathology: Progressive calcification and fragmentation of elastic fibers in skin, eyes, and vessels
• Clinical features:
  • Skin: Yellowish papules ("plucked chicken skin") on neck, axillae, flexural areas
  • Eyes: Angioid streaks (breaks in Bruch's membrane), macular degeneration, retinal hemorrhages
  • Vascular: Premature atherosclerosis, peripheral arterial disease, coronary artery disease
  • Stroke (ischemic), GI hemorrhage, hypertension
  • Typically middle-aged females; estrogen may worsen skin lesions
• Diagnosis: Skin biopsy (fragmented, calcified elastic fibers); fundoscopy (angioid streaks); genetic testing
• Treatment: Aggressive cardiovascular risk factor management; intravitreal anti-VEGF for macular neovascularization; avoid trauma, contact sports

Large Artery Diseases

Moyamoya Disease/Syndrome

• Genetics: Multiple loci identified; RNF213 (17q25) most common in East Asian populations; ACTA2, GUCY1A3 in other forms
• Pathology: Progressive stenosis/occlusion of distal internal carotid arteries and proximal MCA/ACA → compensatory collateral network ("puff of smoke" on angiography)
• Clinical features:
  • Bimodal age distribution: Children (ischemic strokes, TIAs triggered by hyperventilation/crying) and adults (hemorrhage more common)
  • Recurrent strokes, TIAs
  • Headaches, seizures, cognitive decline
• Imaging: MRA/CTA: Bilateral ICA stenosis with "ivy sign" and collaterals; conventional angiography: "puff of smoke" appearance
• Diagnosis: Angiographic criteria; genetic testing for familial cases
• Treatment: Surgical revascularization (direct or indirect bypass); antiplatelet therapy; avoid hypotension and dehydration

Homocystinuria

• Genetics: Autosomal recessive; CBS gene (21q22); cystathionine β-synthase deficiency
• Pathology: Elevated homocysteine → endothelial dysfunction, thrombophilia, accelerated atherosclerosis
• Clinical features:
  • Marfanoid habitus (tall, thin), ectopia lentis (downward), intellectual disability
  • Osteoporosis, scoliosis
  • Arterial and venous thrombosis
  • Stroke (large and small vessel), MI, peripheral vascular disease
  • Psychiatric disorders
• Diagnosis: Elevated plasma homocysteine and methionine; urine homocystine
• Treatment: Pyridoxine (B6) — ~50% respond; methionine-restricted diet; betaine; folate, B12 supplementation

Summary Comparison Table

AD = autosomal dominant; AR = autosomal recessive; AC = anticoagulation; BB = beta-blockers; ERT = enzyme replacement therapy; ID = intellectual disability; VPA = valproate; WMH = white matter hyperintensities; MRS = MR spectroscopy; PXE = pseudoxanthoma elasticum

References

1. Dichgans M, et al. CADASIL and other monogenic cerebral small vessel diseases: Recommendations of the European Academy of Neurology. Eur J Neurol. 2020;27(2):255-267.
2. Meschia JF, et al. Management of Inherited CNS Small Vessel Diseases: The CADASIL Example. Stroke. 2023;54:e452–e464.
3. Bushnell CD, et al. 2024 Guideline for the Primary Prevention of Stroke. Stroke. 2024;55:e344–e424.
4. Chabriat H, et al. CADASIL. Lancet Neurol. 2009;8:643–53.
5. Sharma P, Meschia JF, editors. Stroke Genetics. 2nd ed. Springer; 2017.
6. Ginsberg L. Fabry Disease. In: Stroke Genetics. Springer; 2017. p. 105–115.
7. Sproule DM, Kaufmann P. Mitochondrial encephalopathy, lactic acidosis, and strokelike episodes. Ann N Y Acad Sci. 2008;1142:133–58.