Catastrophic Antiphospholipid Syndrome (CAPS) is a very rare and severe form of the antiphospholipid syndrome. In this disorder patients suffer sudden, widespread small vessel blood clots throughout the body. Close to half of those affected die soon after the syndrome begins, even though those who survive the acute stages frequently recover completely and remain well indefinitely. Aggressive treatments have proved lifesaving for some patients, and it is clear that the diagnosis needs to be made promptly, and these special measures instituted rapidly.

The clinical manifestations of CAPS vary from patient to patient, often shutting down major organs such as the intestines, brain, heart, or kidneys. Obstructions in large blood vessels may occur, and a severe lung condition known as acute respiratory distress syndrome (ARDS) can be a major feature early on in many patients. CAPS occurs in less than one percent of patients with previously diagnosed antiphospholipid syndrome, so it is certainly rare. It has sometimes arisen spontaneously as the first manifestation of APS, and with no clinical or serological confirmation of lupus. 

Efforts have been underway to facilitate early diagnosis, raise awareness to start the most effective treatments in a timely manner, and better understand the cause(s) of this extreme condition in order to improve outcomes. A better understanding of this rare syndrome was made possible in 2000, when the European Forum on Antiphospholipid Antibodies supported the startup of an international registry of CAPS patients.

In the most recent report by the CAPS registry group, 40 percent of the patients had systemic lupus along with APS, and 48 percent had APS without any additional autoimmune process (primary APS).  The ratio of women/men was 153/67 which is more similar to primary APS than lupus, which tends toward a 10/1 woman/man ratio in most populations. Blood clots in the kidney were observed in 70 percent of the patients, lung complications in 66 percent, brain involvement in 60 percent, heart complications in 52 percent, and skin manifestations in 47 percent. 

The most important clinical feature of CAPS to recognize is that, despite the high risk early on of this potentially devastating syndrome, the long-term prognosis of those patients who do survive the initial onset appears to be excellent.

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Joan T. Merrill and Ronald A. Asherson, Nature Clinical Practice Rheumatology (2006) 2, 81-89