Behçet's disease and avascular necrosis of the knees: a case report.

Introduction and importance: Behçet's disease (BD) is a rare, autoimmune vasculitis usually characterized by oral and genital ulcers with systemic involvement of multiple organ systems. Its diagnosis is usually clinical as it lacks the disease-specific markers seen in other autoimmune pathologies. Avascular necrosis (AVN) is extremely rare in BD and if it were to occur, it would usually be unifocal. Case presentation: This case report presents an odd case of BD that was complicated by bilateral AVN of the knees in a 36-year-old man. His diagnosis was confirmed by MRI of both knees after he started complaining of knee pain while on rituximab. The patient's treatment was adjusted and he has reported relief from pain and clinical improvement while on Infliximab, which he is currently maintained on. Clinical discussion: AVN is usually observed with chronic steroid use or with diseases such as sickle cell disease. The vasculitis associated with BD may result in an ischemic insult to the bone and joints; however, the pathophysiology is still unclear. Hence, joint pain in BD patients may be a warning sign to AVN which thus needs to be considered among the differential diagnosis in these immunosuppressed patients. Conclusion: This is case of bilateral AVN of the knees in a patient with BD warrants investigation of joint pain or symptoms in patients with BD and other autoimmune diseases even if not on corticosteroid treatment. Prompt evaluation of patients' symptoms decreases risks of development of serious complications and preserves their health.