Clinical characteristics of patients presenting an unexplained dissection of a medium-sized artery and comparison with clinical characteristics of patients with fibromuscular dysplasia

INTRODUCTION Fibromuscular dysplasia (FMD) is a nonatherosclerotic arterial disease with a widely unknown pathophysiology. Dissections have been described as possible complications of this disease. The objectives of this retrospective study are to report the clinical characteristics in patients under 60 years of age who suffered an unexplained dissection of a medium-sized artery and to compare them with those of patients with both proved FMD and dissection(s). MATERIALS AND METHODS We identified two cohorts: the MRC D+ cohort and the EU-FMD D+ cohort. The first one includes 44 patients with unexplained dissection of a medium-sized artery while the second one includes 55 European FMD patients presenting at least one dissection of a medium-sized artery. Subsequently, we compared these two groups regarding several clinical characteristics. RESULTS Compared with the EU-FMD D+ cohort, the MRC D+ cohort includes significantly less women (32% versus 55%, p=0.024), and is characterized by a lower prevalence of aneurisms (7% versus 35%, p<0.001) and a higher stroke prevalence (64% versus 22%, p<0.001), particularly in women. Also, women without established FMD present their first dissection at a significantly younger age than women with FMD (44 +/- 8.9 versus 51 +/- 8.2 years old, p=0.031) and include a significantly higher proportion of current or ancient smokers compared with their counterparts in the EU-FMD D+ cohort (46% versus 17%, p=0.049). CONCLUSION Our study suggests that some subgroups of patients presenting unexplained dissections might share clinical characteristics with FMD patients presenting dissections. An explanation might be that they have a similar pathophysiological mechanism underlying their dissections. Thus, the FMD definition might be enlarged in the long run, with some patients suffering from an unexplained dissection labelled as having “atypical fibromuscular dysplasia”. Further investigation is needed in order to confirm this theory, but if it does, this may lead to an improvement in these patients’ management, particularly regarding initial diagnosis and follow-up. In the future, a new algorithm might be created for the diagnosis of FMD, incorporating some clinical characteristics and non-invasive examinations, such as high resolution echotracking, genetic analysis and blood-based tests.