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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.

The catastrophic antiphospholipid syndrome (CAPS, Asherson's syndrome) develops rapidly following an identifiable triggering factor (eg infection, trauma, inadequate coagulation neoplasia, obstetric) in antiphospholipid antibody positive patients. It is most frequently encountered in patients with a primary antiphospholipid syndrome or systemic lupus erythematosus (SLE) or "lupus-like" disease (LLD). It manifests mainly with small vessel thromboses affecting organs (gastrointestinal tract, brain, heart), large vessel occlusions in one-third, manifestations of the systemic inflammatory response syndrome (SIRS), particularly the acute respiratory distress syndrome (ARDS). The mortality is high, although with early and effective therapies, including full parenteral anticoagulation, corticosteroids, plasma exchanges and IV globulins, an improvement in this high death rate has been noted recently.

An unusual variant of the antiphospholipid syndrome (APS) termed the Catastrophic Antiphospholipid Syndrome (CAPS) in 1992 by Asherson is described. The condition may arise “de-novo” in a patient previously not suspected of having an APS or during the course of a “Primary” APS or Secondary APS (most commonly SLE). The patient may already be on therapy. “Trigger” factors (infections most commonly) have been identified in 45% of patients but in the majority, they remain unidentified. Clinically, the patients present with small vessel occlusions involving organs (e.g. bowel, brain, heart, kidney) but large vessels occlusions do occur. Unusual organs are involved and the clinical features depend on which organs are affected. Because of tissue necrosis, the Systemic Inflammatory Response ensues (“SIRS”) and many patients develop ARDS. Despite seemingly adequate therapy (parenteral heparin, steroids, antibiotics), the mortality remains high (approximately 50%).

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.

Catastrophic antiphospholipid syndrome (CAPS) (Asherson's Syndrome), is a life-threatening condition characterized by a rapidly progressive thromboses resulting in a multiorgan dysfunction syndrome (MODS), evidence of systemic inflammatory response syndrome (SIRS) in the presence of antiphospholipid antibodies. CAPS differs from the classic APS by predominantly affecting small vessels, involvement of unusual organs, rapid onset of MODS, and the development of acute respiratory distress syndrome (ARDS) in 25% of patients, which is a feature of SIRS. Obstetric-related multiorgan failure may be a feature of a subset of CAPS more frequently than was previously thought. Patients with obstetric complications should be tested for antiphospholipid antibodies and genetic thrombophilia in order to institute early prophylaxis. Low-molecular-weight heparin is the drug of choice for preventing obstetric complications and CAPS due to its anticoagulant and anti-inflammatory properties.

The concept of “probable” antiphospholipid syndrome (APS) is almost identical with several conditions which may presage the development of the APS with its major complications of large vessel thromboses resulting in deep vein occlusions in the lower limbs (DVT) particularly and strokes. These conditions comprising livedo reticularis, chorea, thrombocytopenia, fetal loss and valve lesions. These conditions, comprising livedo reticularis, chorea, thrombocytopenia, fetal loss and valve lesions may be followed, often years later by diagnosable APS. The issue whether these patients should be more aggressively treated on presentation in order to prevent the thrombotic complications. A new subset of the APS is proposed viz. microangiopathic antiphospholipid syndrome (“MAPS”) comprising those patients presenting with thrombotic microangiopathy and demonstrable antiphospholipid antibodies who may share common although not identical provoking factors (e.g. infections, drugs), clinical manifestations and haematological manifestations (severe thrombocytopenia, hemolytic anaemia) and treatments viz. plasma exchange. Patients without large vessel occlusions may be included in the MAPS subset. These conditions include thrombotic thrombocytopenic purpura (TTP), hemolytic–uremic syndrome (HUS), and the HELLP syndrome. Patients with catastrophic antiphospholipid syndrome (CAPS) who do not demonstrate large vessel occlusions also fall into this group. Disseminated intravascular coagulation (DIC) has also been reported with demonstrable antiphospholipid antibodies and also manifests severe thrombocytopenia and small vessel occlusions. It may cause problems in differential diagnosis.

The catastrophic antiphospholipid syndrome is characterised by the rapid chronological development of fulminant thrombotic complications that predominantly affect small vessels. It has been reported as frequently occurring in patients with underlying malignancies. We analysed the web site-based international registry of patients with catastrophic APS. The clinical characteristics of patients with CAPS and an underlying malignancy were evaluated. Of the 262 patients included in the CAPS registry, information on associated malignancies was available in 23 (9%) cases. Haematological malignancies were present in 6 (26%) patients. Four of the patients suffered from lung carcinoma (17%), and two patients (9%) from colon carcinoma. In most of the patients (61%), malignancy was the precipitating factor for CAPS. In 4 patients (17%), however, surgical procedures related to the carcinoma were noted as precipitating factors. In one patient CAPS occurred during allogenic stem cell transplantation after diagnosis of acute lymphoblastic leukemia (ALL). Cerebral manifestations were most common and consisted mainly of cerebral infarcts and encephalopathy. Recovery occurred in 9/23 (39%) patients. Malignancy may be an important risk factor for CAPS. 9% of patients with CAPS presented with an underlying malignancy. In most of these patients, the malignancy and/or surgical procedures were the precipitating factors for CAPS.