Paget-Schrotter Syndrome (PSS) also known as “effort thrombosis” is a form of primary thrombosis in the subclavian vein at the costoclavicular junction is usually seen in younger patients after repeated strenuous activity of the shoulders and arms. When occurring in younger patients, PSS presents itself with predisposing factors such as unilateral dull, aching pain in the shoulder or axilla and swelling of the arm and hand.

We report a rare case of unusual left axillo-subclavian vein thrombosis in absence of clear risk factors and a negative hypercoagulable workup in a 36-year-old Hispanic woman who presented with 2 days duration of left upper extremity pain and swelling after a week of heavy exercise in aerobic class. Very few documented cases of primary or spontaneous ASVT in absence of clear factors and in such anatomical location have been previously reported.

The patient was started on strict precautions of left upper extremity immobilization, analgesics in the form of Tylenol 650 mg every 6 h for pain as well as cold compresses. Lovenox 90 mg subcutaneous twice daily (1 mg/kg BID) was started together with warfarin to keep INR 2–3.

In addition to the unusual location in the left upper extremity in our case, the absence of common etiologic factors makes our case of Paget-Schroetter Syndrome a very unique one. Presently, there is a lack of guided management of rare conditions such as our case, or consensus among the sources. Physicians should be aware of this rare disease since untreated conditions may be debilitating for the patient and very costly especially if diagnosed with a delay.