Unraveling Vascular Mysteries: A Case Report of Fibromuscular dysplasia associated renal infarcts mimicking Vasculitis

Summary: Background: Fibromuscular dysplasia (FMD) and vasculitis are two distinct vascular disorders with overlapping clinical presentations, making accurate diagnosis challenging. We present a compelling case study highlighting the importance of early differentiation between FMD and vasculitis, demonstrating the potential consequences of misdiagnosis and the subsequent journey towards appropriate management. Case Presentation: A 67-year-old female, with a history of erythema nodosum since the age of 17 years and hypertension, presented to the emergency room in December 2023 with severe acute abdominal pain. This onset followed a recent episode of COVID-19 pneumonia. Admitted for evaluation, a computerized tomography (CT) abdomen revealed reduced flow to bilateral kidneys with wedge-shaped defects consistent with bilateral renal infarcts and acute thrombosis. Renal angiograms showed right renal artery stenosis with a non-occlusive clot and left renal artery with moderate stenosis and distal small segmental branch clot. The patient was started on Apixaban 5 mg twice daily for renal thrombosis. Subsequent investigations for autoimmune vasculitis showed positive results for anti-phosphatidylserine IgM and IgG, while the remainder of the vasculitis workup was extensively negative. Given the background of erythema nodosum and these CT findings, suspicion for medium to large vessel vasculitis was high, prompting initiation of IV steroids. However, steroids led to steroid psychosis, necessitating discontinuation and initiation of Mycophenolic acid 500 mg twice daily. Discharged with follow-up in the rheumatology outpatient clinic, further extensive investigations returned negative results. She also established care with nephrology who continued the patient on Apixaban and Mycophenolic acid. She was also advised a repeat imaging study including pan CT with and without contrast. Six months post the initial episode, a repeat CT revealed beading in cervical, carotid, vertebral, and bilateral renal arteries, compatible with multifocal fibromuscular dysplasia (FMD). Referral to a vascular medicine specialist ensued, who reviewed all investigations. Given the absence of any supportive inflammatory markers, and the CT angiography suggestive of FMD, the vascular medicine specialist ultimately confirmed the diagnosis of FMD and discontinued medications including Apixaban and Mycophenolic acid. The patient was started on Aspirin and statins for stroke prevention, considering it a high-risk complication for FMD. Figure 1: CT abdomen with angiography: Broken arrow depicting beading in the left renal artery, solid arrow indicating left renal necrosis. Figure 2: CT abdomen with angiography: Arrow indicating beading in the right renal artery. Discussion: The presented case underscores the intricate diagnostic landscape when differentiating fibromuscular dysplasia (FMD) from vasculitis, highlighting the necessity for a comprehensive evaluation and collaborative approach. Key challenges surfaced due to overlapping clinical features of FMD and vasculitis, compounded by the patient's history of erythema nodosum and recent COVID-19 pneumonia. The initial presentation of acute abdominal pain further complicated diagnosis, as both conditions can manifest with visceral ischemia and thrombotic events. Additionally, the potential for falsely elevated inflammatory markers secondary to COVID-19 infection added a layer of complexity to interpretation. Diagnostic imaging played a pivotal role, initially suggesting vasculitis with findings of renal infarcts and thrombosis. However, subsequent imaging revealed arterial beading in various locations, prompting reconsideration towards FMD. This underscores the importance of serial imaging and ongoing reassessment in cases of diagnostic uncertainty. Management challenges arose, exemplified by complications from empiric steroid therapy and delayed initiation of appropriate treatment. The use of Mycophenolic acid and other immunosuppressants poses significant concerns due to their high risk of immunosuppressive side effects. While these medications may be effective in managing certain autoimmune conditions, their broad suppression of the immune system can leave patients vulnerable to infections and other complications. Ultimately, targeted therapy with aspirin and statins was initiated, emphasizing the importance of individualized management strategies. Conclusion: In conclusion, the presented case highlights the diagnostic intricacies and therapeutic challenges inherent in distinguishing between FMD and vasculitis. Through a comprehensive clinical approach, including serial imaging studies and interdisciplinary collaboration, clinicians can navigate the complexities of vascular disorders and tailor individualized treatment strategies to avoid unnecessary medications and improve patient outcomes.