Unusual Vascular Claudication in a Seronegative Patient: Raynaud's Phenomenon or Atypical Buerger Disease.

We report a diagnostically challenging case of progressive upper‑extremity ischemia in a 31‑year‑old non‑smoking woman whose presentation defied classic criteria for thromboangiitis obliterans (TAO), Raynaud's phenomenon (RP), or small‑vessel vasculitis. Despite initial imaging suggesting brachial artery stenosis, repeat computed tomography angiography (CTA), ultrasound, and angiography demonstrated patent proximal vessels with sluggish distal forearm flow and diminutive radial and ulnar arteries at the wrist, consistent with terminal small‑vessel disease. Extensive hypercoagulable and vasculitis workup was unrevealing, and inflammatory markers remained normal. The patient's symptoms progressed from intermittent discoloration and pain to persistent ischemia, ultimately improving only after prostacyclin infusion, suggesting underlying microvascular dysfunction. Her atypical demographic profile-female sex, absence of tobacco exposure, isolated upper‑extremity involvement-and lack of systemic features created diagnostic ambiguity, raising consideration of atypical TAO, severe secondary RP, or seronegative vasculitis. This case highlights the importance of maintaining broad diagnostic suspicion and individualized management in patients with unexplained distal ischemia and nondiagnostic serologic and imaging findings.