E030 Osteonecrosis of the spine in antiphospholipid antibody syndrome
Authors: Shah Meera , Putchakayala Kiran 
Published: April 2024

Abstract

Background/Aims
Osteonecrosis (ON) is a well-known complication of several rheumatic diseases, affecting the hip, knee, shoulder, or ankle. The involvement of spine and other sites with ON has been reported with catastrophic APS, although the nature of this association is not completely clear. In antiphospholipid syndrome, thrombosis of blood vessels is considered a possible mechanism, along with other risk factors, such as active disease, thrombocytopenia, glucocorticoid use and associated autoimmune diseases, making the pathophysiology multifactorial. We report a case of a 66-year-old male with APS who developed bone infarcts/osteonecrosis after withdrawal of anticoagulation for APS, which was necessitated by a bleeding complication and introduction of steroids for immune thrombocytopenia.

Methods
A 66-year-old male came to us with history of unprovoked deep vein thrombosis (DVT) for which he was on antiplatelet and anticoagulation for over 20 years. He was diagnosed to have high titre anti cardiolipin antibody (ACA)(186 U/ml) without other autoimmune conditions. He had an episode of bladder hematoma in August 2022, needing his anticoagulation to be suspended temporarily. He was also found to have profound thrombocytopenia with raised inflammatory markers. Considering it to be immune mediated he was started on high dose oral corticosteroids and was later maintained with azathioprine while the oral prednisolone dose was gradually brought down to 10 mg daily in about 3 months’ time. His thrombocytopenia improved progressively however he developed an unprovoked DVT in October 2022 and was restarted on anticoagulation. He continued to have low dose steroids for about 6 months. Meanwhile, he started having a new onset of low back pain in December 2022. An MRI of the whole spine showed multilevel osteonecrosis with haemorrhagic cavities in a few vertebral bodies.

Results
This case highlights three interesting points. The first is the atypical presentation of the osteonecrosis involving vertebral bodies. Osteonecrotic lesions in the spine of a patient with catastrophic primary antiphospholipid syndrome has been reported. Our case signifies that although vertebral bodies are an uncommon site for avascular necrosis in patients with APS, it is not rare. Secondly, the pathogenesis of ON is complex. Whether ACA are directly responsible for this condition or whether they are the bystanders remains controversial. ACA have shown to be an independent risk factor for developing ON in many studies. Thirdly, steroids are known to be an important risk factor in patients presenting with osteonecrosis. The vascular compromise could be attributed to a steroid induced hypercoagulative state, abnormal lipid metabolism, or fat embolism.

Conclusion
ON in APS is unusual and its underlying pathophysiology remains multifactorial. However, when complicated by the high ACA levels, active disease, difficult anticoagulation (bleeding tendencies), thrombocytopenia or prolonged use of steroids, it can lead to hypercoagulable state causing micro thrombosis and avascularisation.

Disclosure
M. Shah: None. K. Putchakayala: None.