Introduction Cigarette smoking is a modifiable risk factor associated with intracranial aneurysms (IAs) formation and rupture. Cytochrome P450 2A6 (CYP2A6) is the main enzyme implied in nicotine and xenobiotics catabolism.

Aim of Study Our study aimed to investigate the associations between specific single-nucleotide polymorphism (SNPs) of the CYP2A6 gene and the presence of single or multiple sporadic IAs as well as their rupture with respect to the smoking habit.

Methods 331 Italian patients with sporadic IAs were recruited in a single Institution. We recorded data about the number of aneurysms, clinical onset with subarachnoid hemorrhage (SAH), and smoking habits. Genetic analysis was performed on peripheral blood samples: CYP2A6 *B2, CYP2A6 *2, and CYP2A6 *14 SNPs were analyzed in the patients‘ group, and in 150 healthy control subjects. Statistical analysis was conducted according to genetic association studies guidelines.

Results The frequency of aSAH was higher in smokers than non-smokers (98% vs 70%), regardless of the CYP2A6 SNPs pattern. There was a significant correlation between IA rupture and tobacco consumption in patients with the heterozygous CYP2A6 *B2 allele (p=.00001). Alla patients carrying the heterozygous CYP2A6 *14 allele had an aSAH event (100%), independently of smoking habits.

Conclusion A cigarette smoker carrying a fully active CYP2A6 enzyme (heterozygous *B2 allele) may have an increased risk of IA rupture, compared to people having functionally less active variants: further investigation on a larger sample is needed to verify this result. The role of the heterozygous CYP2A6 *14 allele in aSAH is yet to be clarified.

Disclosure of Interest Nothing to disclose