Mr. H, aged 17 years, was brought in to see his primary-
care provider after experiencing pain when he manipulated his right arm. He presented and was examined by the pediatric nurse practitioner (NP), who confirmed right axilla pain that increased when Mr. H was weightlifting and raising his arm over his head.

The pain started two weeks ago, after the patient returned to his weightlifting routine at the gym. (The teenager had stopped weight-training for a brief period of time.) Mr. H reported that the pain was dull and constant, but that it did not cause him to limit his daily activities. 

1. History

Mr. H’s history was unremarkable for any significant childhood illnesses. His immunizations were up-to-date. The young man was a smoker and attended vocational school. He denied illicit-drug use and excessive alcohol consumption, but admitted to having used anabolic steroids in the past. His family history was unremarkable.

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2. Examination

Mr. H was a pleasant teenager who, on examination, immediately complained of significant tenderness in the right axilla. The tenderness was noted on palpation at the mid-axillary junction, without lymph node tenderness or swelling to the pectoralis major or latissimus dorsi muscles. Full range of motion was noted in the arms and shoulders bilaterally, and bilateral strength was also equal. 

After initial presentation, Mr. H was encouraged to return to the gym. A modified weight-lifting routine was recommended, and Mr. H was instructed to apply ice to the affected area after training. In addition, the NP ordered a nonsteroidal anti-inflammatory medication for residual pain. 

Two days later, Mr. H returned to the clinic noting that the pain was not subsiding. At this point, Dr. R—the on-call physician—evaluated Mr. H. Dr. R diagnosed myositis and prescribed 60 mg of prednisone once daily for five days and 800 mg ibuprofen every eight hours. Ten days later, the patient presented with redness and swelling of the right arm. An ultrasound was ordered at that time, and the teen was admitted to the regional pediatric center with a diagnosis of deep vein thrombosis (DVT) of the right subclavian vein. 


3. Differential diagnosis

Initially, there were several diagnoses to consider, including tendinitis, myositis, superior vena cava syndrome, upper-extremity DVT, antiphospholipid syndrome, and clotting disorder. 

4. Laboratory Data and Diagnosis

The initial ultrasound revealed several clots to the right subclavian vein. Mr. H’s platelet count was low at 
90,000/µl and partial thromboplastin time (PTT) was elevated at 45 seconds.

At the two-month follow- up with the hematologist, the patient’s platelet count increased to 187,000/µl and antifactor Xa (anti-Xa) was within normal limits at 0.96 IU/mL. Additional labs ordered two months later were remarkable for lupus anticoagulant panel with a prolonged prothrombin time of 16 seconds, and a prolonged PTT of 46 seconds.

The PTT did not correct with 1:1 mixing. A dilute Russell Viper Venom Time (dRVVT) screen was prolonged and the dRVVT ratio was high. The hexagonal phospholipid neutral study was positive at 25 seconds, and the platelet neutralization study was also high. Anticardiolipin immunoglobulin (Ig) G antibodies were elevated. IgM and IgA levels were negative. A heparin anti-Xa level was therapeutic at 0.91 IU/mL.

A magnetic resonance angiogram and a magnetic resonance venogram of the right upper extremity revealed fixed focal narrowing of the right subclavian vein distal to the head of the clavicle, with the arms raised and at the patient’s side, congruent with the diagnosis of thoracic outlet syndrome. There were no arterial abnormalities, and no additional thrombus was noted.