Thoracic Outlet Syndrome Presenting With Unilateral Upper Extremity Venous Congestion: A Diagnostic Role for Dermatology.

Thoracic outlet syndrome (TOS) is a constellation of symptoms associated with compression of the neurovascular bundle of the brachial plexus or subclavian vessels. TOS can be classified as neurogenic, arterial, or venous depending on the structure that is compressed. Symptoms include arm pain, swelling, fatigue, paresthesia, weakness, and discoloration of the hand. While neurogenic and vascular symptoms are well described, cutaneous manifestations of TOS are less often described. We present the case of a 43- year-old woman with acute right upper extremity (RUE) pain, swelling, and progressive erythema with venous engorgement. Initial workup included Doppler ultrasound, coagulation studies, and D-dimer to rule out deep vein thrombosis (DVT), which were all negative. CT chest with contrast revealed no evidence of a thrombus in the right subclavian vein or dilated collateral veins. Rheumatology suspected superficial thrombophlebitis, suggested warm compresses, and RUE elevation. Dermatology was subsequently consulted and identified a constellation of cutaneous signs, including palmar erythema, prominent superficial venous distension on the RUE, petechiae, and pitting edema. These findings prompted repeat vascular evaluation, and venous duplex ultrasonography confirmed venous TOS (vTOS), for which surgical management was scheduled. This case highlights the diagnostic importance of dermatologic assessment in systemic vascular disorders. Cutaneous changes such as unilateral erythema, venous engorgement, temperature asymmetry, and petechiae may represent early indicators of vTOS, yet are frequently misinterpreted as infectious, rheumatologic, or thrombotic conditions. Incorporating dermatologic clues with vascular examination and targeted imaging may reduce misdiagnosis and expedite definitive management.