Small vessel occlusions may occur as part of the vascular manifestations of the Antiphospholipid Syndrome (APS) and may affect glomerular, skin, retinal, bowel, hepatic or pulmonary vessels. These thrombotic lesions are proven (usually by biopsy, surgical procedures, at autopsy or by specialized techniques e.g. in the case of retinal vascular occlusions). Another group of small vessel occlusions remain unproven and include osteonecrosis, hearing loss and a variety of brain syndromes. All these constitute the microvascular manifestations of the APS. Another separate group exists viz. thrombotic microangiopathic antiphospholipid-associated syndromes including Thrombotic Thrombocytopenic Purpura (TTP), HELLP syndrome and the thrombotic microangiopathies (primary or secondary e.g. to SLE itself or lupus-like disease). There is an accompanying haemolytic anaemia, often thrombocytopenia and presence of schistocytes. There are no large vessel occlusions and the antiphospholipid antibodies (aPL) may be generated by endothelial damage. It is possible that some of these "non-pathogenic" aPL may be rendered pathogenic by factor(s) unknown at this time causing a disturbance of the haemostatic equilibrium with resultant large vessel occlusions. This may be occurring in patients with the catastrophic antiphospholipid syndrome (CAPS/Asherson's syndrome). The term "MAPS" is suggested for these two groups of conditions.