Intracranial aneurysms occur in 8% of individuals with autosomal-dominant polycystic kidney disease and 7% with cervical fibromuscular dysplasia.105,106 Ehlers-Danlos type IV is associated with dissection of verte- bral and carotid arteries, carotid-cavernous fistulas, and intra- Loss-of-function mutations in KRIT1, malcavernin, and PDCD10 genes cause cerebral cavernous malformation syn- Mutations in can cause inherited cerebral amyloid angiopathy syndromes.109 Genetic Factors: Summary and Gaps The cause of ischemic stroke remains unclear in as many as 35% of patients. The use of DNA sequence information, in conjunction with other omics (eg, transcriptomics, epig- enomics) and clinical information to refine stroke origin, although promising, has not yet proven useful for guiding preventive therapy. Genetic factors could arguably be clas- sified as potentially modifiable, but because specific gene therapy is not presently available for most conditions, genetic factors have been classified as nonmodifiable. It should be recognized that treatments are available for some, such as Fabry disease and SCD. Genetic Factors: Recommendations 1. Obtaining a family history can be useful in identify- ing people who may have increased stroke risk (Class IIa; Level of Evidence A). 2. Referral for genetic counseling may be considered for patients with rare genetic causes of stroke (Class IIb; Level of Evidence C). 3. Treatment of Fabry disease with enzyme replacement therapy might be considered, but has not been shown to reduce the risk of stroke, and its effectiveness is unknown (Class IIb; Level of Evidence C). 4. Noninvasive screening for unruptured intracranial aneurysms in patients with 2 first-degree relatives with SAH or intracranial aneurysms might be rea- sonable (Class IIb; Level of Evidence C).110 5. 