Abstract Body (Do not enter title and authors here): Introduction/Background:
Fibromuscular Dysplasia (FMD) is a non-atherosclerotic vascular disease that primarily affects medium-sized arteries and is characterized by abnormal cell development in the artery walls. Recent studies have suggested that various connective tissue features may be prevalent in patients with FMD, however the clinical significance of these findings on the disease course are uncertain.

Research Questions/Hypothesis:
We hypothesized that the presence of connective tissue features in patients with FMD might indicate a more severe disease course, potentially associated with increased severity of vascular complications.

Goals/Aims:
To evaluate the association between connective tissue features and the severity of vascular complications in FMD patients on outcomes including dissections and stroke.

Methods/Approach:
This cross-sectional study involved 2,454 patients diagnosed with FMD at a tertiary referral center. Patients were classified into two groups based on the presence (n=324) or absence (n=2130) of connective tissue features (pectus deformity of any kind, scoliosis, pneumothorax, inguinal hernia, uterine rupture, bowel perforation, Achilles tendon rupture). We evaluated the incidence of dissections and ischemic or hemorrhagic strokes using odds ratios and chi-squared tests.

Results/Data:
The cohort consisted of 2,454 participants with an average age of 64.8 years, of whom 89.1% were female and 92.4% identified as White. When comparing groups with and without connective tissue features, there were no significant differences in the prevalence of aneurysms at any site. Among the subgroup of FMD patients with connective tissue features (n=234), prevalent conditions included pectus (12.35%), scoliosis (47.22%), pneumothorax (16.67%), inguinal hernia (13.58%), uterine rupture (16.36%), bowel perforation (6.48%), and Achilles tendon rupture (1.85%). Vascular outcome analysis showed significant differences: the odds of experiencing a stroke were higher in patients with these features (odds ratio: 1.60; P-value: <0.01), whereas the odds of experiencing dissections were lower (odds ratio: 0.77; P-value: 0.03).

Conclusion:
The presence of connective tissue features in patients with FMD is associated with 60% higher odds of experiencing a stroke, equivalent to a 1.6-fold increase, compared to those without these features. This association may represent a novel finding in the literature, warranting further investigation.