Rare Systemic Vasculitides: Polyarteritis Nodosa and Takayasu Arteritis.

BACKGROUND Polyarteritis nodosa (PAN) and Takayasu arteritis (TA) are systemic medium- and large-vessel vasculitides associated with significant morbidity when diagnosis is delayed. Although described in the literature, reports directly demonstrating the impact of diagnostic timing on vascular outcomes remain limited. This report presents 2 rare and contrasting cases highlighting the importance of early recognition with timely vascular and immunosuppressive interventions, which can prevent irreversible ischemic complications, whereas delayed diagnosis can result in permanent structural damage, reinforcing the need for accurate differentiation between PAN and TA. CASE REPORT Case 1 was a young woman with refractory hypertension and significant vascular manifestations, in whom PAN was diagnosed through combined analysis of symptoms, laboratory tests, and angiographic findings. Early angioplasty and treatment with glucocorticoids and azathioprine resulted in a favorable response. Case 2 was a woman with TA who had extensive involvement of the aorta and its branches with irreversible sequelae, including aortic valve replacement. Diagnostic delay led to progression. Glucocorticoids and adalimumab achieved clinical stabilization without reversing established structural damage. CONCLUSIONS The presented cases reinforce the importance of early identification and appropriate differentiation of systemic vasculitides to prevent irreversible vascular lesions. This study compares a case of PAN diagnosed early, with vascular intervention preventing ischemic complications, and a case of TA diagnosed late, with permanent structural damage despite treatment. Early use of vascular imaging combined with prompt immunosuppressive therapy and multidisciplinary management contributes to a favorable prognosis, highlighting the need for greater clinical awareness and careful diagnostic strategies in rare vasculitides.