Anti-phospholipid syndrome leading to digital ischaemia and rare organ complications in systemic sclerosis and related disorders.

Antiphospholipid syndrome (APS) is an acquired, autoimmune thrombophilia that can occur as a primary disorder (with no associated disease) or secondary to infection, medication usage and autoimmune rheumatic diseases (ARDs). The association between APS and systemic lupus erythematosus (SLE) is well established, and practicing rheumatologists check for APS antibodies in the routine assessment of SLE, particularly if clinical features such as thrombotic events or pregnancy loss are present. APS secondary to systemic sclerosis (SSc)-related disorders is less widely recognised and easily overlooked. We describe 5 cases that highlight the varied breadth of clinical manifestations of APS in the context of SSc and related disorders. These cases range from uncomplicated Raynaud's phenomenon, digital ulceration/necrosis, critical digital ischaemia/gangrene and rare internal organ complications of APS in SSc-spectrum disorders. To our knowledge, our cases include the first reported case of secondary APS contributing to digital necrosis in the context of RACAND syndrome (Raynaud's phenomenon, anti-centromere antibodies and necrosis of the digits) and the first reported case of secondary APS in SSc causing posterior reversible encephalopathy syndrome (PRES). The case series is accompanied by a comprehensive review of the literature relevant to each case. Rheumatologists should be alert to the possibility of APS in SSc-spectrum disorders and should routinely check APS antibodies in all patients at diagnosis, and again later in the disease course if new features emerge that could indicate the presence of thrombotic events or other recognised APS manifestations. Key points • APS should be considered in all patients with digital ischaemic symptoms. • APS may be an important driver of SSc-related digital ulceration/necrosis. • Identification of SSc-associated APS opens up new therapeutic options for acute management and secondary prevention.