Diagnosis
On Doppler ultrasound there was thrombosis of the right tibial and peroneal vein. Paracentesis of the arthritic fluid revealed 18.000/mm3 leukocytes (98 percent were neutrophils), a high protein level: 4,5 gr/dl, increased lactic dehydrogenase levels: 2.603 IU/l and low glucose levels: 48 mg/dl. Culture of the arthritic fluid yielded Streptococcus pyogenes. Cytology was negative for malignant cells.

Due to allergy to penicillin the patient was commenced on clindamycin intravenously with prompt clinical improvement. Laboratory indices returned as well to normal. Low molecular weight heparin (tinzaparin) was administered for the deep venous thrombosis. A thrombophilic screen including (antithrombin III, protein C, protein S, factor V Leiden, anticardiolipin antibodies, antiphospholipid antibodies, lupus anticoagulant, factor II, VII and VIII) did not reveal any thrombophilic disease. The thrombophilic screen is going to be repeated after complete resolution of the infection. The following tests were normal as well: rheumatoid factor, antinuclear antibodies, anti-dsDNA antibodies, anti-ENA screen (anti-SSA, anti-SSB, anti-Sm, anti-Scl70, anti-Jo1), Wright agglutination, antibodies against Borrelia burgdorferi, HbsAg, anti-HCV, anti-streptolysin titre, C3 and C4 complement components and serum protein electrophoresis. A transthoracic echocardiogram was normal.

Teaching points
- Septic arthritis remains one of the medical emergencies that the general physician and the infectious disease specialist alike have to rule out when they encounter a patient with fever and signs of inflammation of a joint. Deep venous thrombosis is another ailment necessitating prompt diagnosis and treatment. Rarely has an association of septic arthritis with deep venous thrombosis been reported in the literature. In such a case report the thrombosis was not in an adjacent area but in another anatomical site. 1

- Other rheumatological diseases such as Behcet's disease, rheumatoid arthritis and systemic lupus erythematosus has been reported in association with thrombosis. The presence of antiphospholipid antibodies in these diseases has been implicated in the pathogenesis of the thrombotic events, but results from various studies have been conflicting.2, 3 In these ailments thrombosis occurs usually in an area remote to the site of the arthritic involvement. Baker's cyst is another relatively common orthopedic disease leading to pain in the posterior aspect of the knee joint and the calf and associated signs of pseudothrombosis. While in the majority of cases with Baker's cyst there is no evidence of thrombus on radiological imaging, one has to bear in mind the coexistence of the two entities. 4

- Our patient's case is unique in that a concomitant manifestation of arthritis and thrombosis in the same topography and at the same time was evident from the outset. The postulated mechanism is that the infection per se through pressure effect on the juxtaposed vasculature was the cause of the deep venous thrombosis in accordance with the data obtained by the MRI. A similar mechanism (through pressure effect) has been described in injuries of the joint and in neuropathic arthropathy with increased arthritic fluid. 5, 6

- Infectious processes in various anatomical sites can extend and lead to thrombosis of adjacent venous vessels. 7 Thus, an infection of the ovary can extend to the neighboroughing ovarian vein and an infection of the mastoid can lead to sigmoid sinus thrombosis. 8 In these infections heparin treatment has been used in association with the antibiotic therapy and the general supportive care. 9

- In conclusion, our case report suggests that physicians have to look for signs of accompanying thrombosis when they evaluate a patient with septic arthritis and vice versa, especially when edema is not confined to the joint.

References
1. Letts M, Lalonde F, Davidson D, Hosking M, Halton J. Atrial and venous thrombosis secondary to septic arthritis of the sacroiliac joint with hereditary protein C efficiency. J Pediatr Orthop 1999;19:156-160
2. Olech E, Merrill JT. The prevalence and clinical significance of antiphospholipid antibodies in rheumatoid arthritis. Curr Rheumatol Rep 2006;8(2):100-8
3. El-Ageb EM, Al-Maini MH, Al-Shukaily AK, Al-Farsi Y, Richens ER. Clinical features of Behcet's diseases in patients in the Sultanate of Oman; the significance of antiphospholipid antibodies? Rheumatol Int 2002;21:176-181
4. Volteas SK, Labropoulos N, Leon M, Kalodiki E, Nicolaides AN. Incidence of ruptured Baker's cyst among patients with symptoms of deep vein thrombosis. Br J Surg 1997;84:342
5. Friedman SA, Doshi R, Patel R, Hedayati R. Venous occlusion secondary to subluxation of the shoulder-a case report. Angiology 1992;43:866-8
6. Tristano AG, Willson M, Montes de Oca. Axillary vein thrombosis as a manifestation of rapidly progressive neuropathic arthropathy of the shoulder associated with syringomyelia. Mayo Clin Proc 2005;80:416-418
7. Masterson T, El-Hakim H, Magnus K, Robinson J. A case of the otogenic variant of Lemierre's syndrome. International Journal of Pediatric Otorhinolaryngology 2005;69:117-122
8. Gourlay M, Guttierez C, Chong A Robertson R. Group A Streptococcal Sepsis and ovarian thrombosis after an uncomplicated vaginal delivery. JABFP 2001:14:375-380
9. Falagas ME, Vardakas KZ, Athanasiou S. Intravenous heparin in combination with antibiotics for the treatment of deep vein septic thrombophlebitis:a systematic review European Journal of Pharmacology (in press)

Acknowledgement
This case was prepared for our web site by Petros I. Rafailidis MD, MRCP UK, MSc, and Anastasios Kapaskelis MD. The case was also submitted for publication.