Antiphospholipid syndrome overview

# Overview
Antiphospholipid syndrome (APS or APLS) or antiphospholipid antibody syndrome is a disorder of coagulation, which can causes blood clots (thrombosis) in both arteries and veins, as well as pregnancy-related complications such as miscarriages, preterm deliveries, or severe preeclampsia. The syndrome occurs due to the autoimmune production of antibodies against phospholipid (aPL), a cell membrane substance. In particular, the disease is characterized by antibodies against cardiolipin (anti-cardiolipin antibodies) and 2 glycoprotein I.
The term "primary antiphospholipid syndrome" is used when APS occurs in the absence of any other related disease. APS is commonly seen in conjunction with other autoimmune diseases; the term "secondary antiphospholipid syndrome" is used when APS coexists with other diseases such as systemic lupus erythematosus (SLE). In rare cases, APS leads to rapid organ failure due to generalized thrombosis and a high risk of death; this is termed "catastrophic antiphospholipid syndrome".
Antiphospholipid syndrome is sometimes referred to as Hughes syndrome after the rheumatologist Dr. Graham R.V. Hughes (St. Thomas' Hospital, London, United Kingdom) who worked at the Louise Coote Lupus Unit at St Thomas' Hospital in London.

# Historical Perspective
In the early 1980s, the term antiphospholipid syndrome was coined to describe a unique form of autoantibody-induced thrombophilia. In 1999, Sapporo classification criteria for APS was published. In 2006, the preliminary Sapporo criteria was revised with the inclusion of anti-2 glycoprotein I (GPI) antibodies in the diagnostic criteria.

# Classification
Antiphospholipid syndrome (APS) can be divided into primary and secondary APS.

# Pathophysiology
Antiphospholipid syndrome (APS) is an autoimmune disease in which antiphospholipid antibodies (anti-cardiolipin antibodies and lupus anticoagulant) react against proteins that bind to anionic phospholipids on plasma membranes. This syndrome can be classified into primary (no underlying disease state) and secondary (in association with an underlying disease state) types. The underlying mechanism of APS mediated by the antibodies is mainly mediated via their affect on the coagulation cascade which subsequenlty leads to increased vascular tone of thrombosis. CAPS is a subclass of APS that results in development of a catastrophic illness characterized by progressive, severe arterial and venous thrombosis in multiple organs, often leading to death.

# Causes
Antiphospholipid syndrome can occur idiopathic or due to autoimmune diseases, certain drugs, infections and malignancies.

# Differentiating Antiphospholipid syndrome from other Diseases
Antiphospholipid syndrome should be differentiated from conditions such as hemolytic uremic syndrome-thrombotic thrombocytopenic purpura (HUS-TTP), disseminated intravascular coagulation (DIC), and vasculitis .

# Epidemiology and Demographics
The incidence of antiphospholipid syndrome (APS) is approximately 5 cases per 100,000 persons per year. The prevalence of APS is approximately 40-50 cases per 100,000 persons worldwide. APS due to systemic lupus erythematosus (SLE) is more commonly seen in the African American and Hispanic population. Middle aged women are more commonly affected by APS than males.

# Risk Factors
The most common risk factors of antiphospholipid syndrome are history of autoimmune diseases like SLE, sjogren's syndrome, infections- cytomegalovirus, human immunodeficiency virus, parvovirus B-19, hepatitis C virus, lyme's disease, syphilis, E.coli, leptospirosis, medications such as hydralazine, quinidine, phenytoin, and amoxicillin, family history- antiphospholipid syndrome is common in patients with a family history of antiphospholipid syndrome.

# Natural History, Complications and Prognosis
If left untreated, 90% of patients with antiphospholipid syndrome (APS) progress to develop recurrent thrombotic or thromboembolic events such as pulmonary embolism, Stroke, Transient ischemic attack, Deep vein thrombosis. The complications caused by APS are mainly thrombotic, neurological, obstetrical, pulmonary and ocular. APS is associated with increased morbidity and mortality. The mean age of death is 59 years.

# Diagnosis

## Diagnostic Criteria
The diagnosis of Antiphospholipid syndrome is made in case of a clinical event (vascular thrombosis or pregnancy event) and repeated positive tests of aPL performed 12 weeks apart (repeat aPL testing is necessary due to the naturally occurring presence of transient low levels of aPL following infections).

## History and Symptoms
Antiphospholipid syndrome can cause (arterial/venous) blood clots (in any organ system) or pregnancy-related complications (especially miscarriages in the second or third trimester). In APS patients, the most common venous event is deep vein thrombosis of the lower extremities (blood clot of the deep veins of the legs). The most common arterial event is a stroke. Patients presenting with antiphosphoplipid syndrome have a positive history of deep venous thrombosis, myocardial infarction and stroke. Last trimester miscarriages, history of heart murmurs or cardiac valvular vegetations and hemolytic anemias may also be present.

## Physical Examination
Physical examination shows no pathognomonic physical findings of antiphospholipid syndrome (APS); however, abnormal features may be found on examination that are related to infarction or ischemia of the skin, viscera, or the central nervous system leading to cutaneous and neurological manifestations.

## Laboratory Findings
Antiphospholipid syndrome (APS) is tested for in the laboratory by both liquid phase coagulation assays (lupus anticoagulant) and solid phase ELISA assays (anti-cardiolipin antibodies). Antibodies found in the plasma os patients with APS are lupus anticoagulant, anticariolipin (aCL), beta-2 glycoprotein I, anti-phosphatidylserine antibodies, anti-prothrombin antibodies. The criteria for testing antiphospholipid antibodies in the plasma is postivity on 2 or more occasion at least 12 weeks apart.

## Chest X Ray
There are no chest X-ray findings associated with antiphospholipid syndrome.

## CT Scan
CT imaging helps to confirm a thrombotic events occuring in antiphospholipid syndrome (APS) such as stroke or pulmonary embolism.

## Echocardiography or Ultrasound
Two dimensional echocardiogram may show aortic or mitral valve insufficiency, which is the most common valvular defect in patients with Libmann Sacks endocarditis.

## Other Imaging Findings

# Treatment

## Medical Therapy
The mainstay of treatment in antiphospholipid syndrome(APS) is anticoagulation. Platelet inhibition is often achieved with aspirin, while warfarin and heparin are the preferred drugs for anticoagulation. Typically, there is no indication for primary prophylaxis. Immunosuppression, the use of intravenous immunoglobulin, and plasmapheresis have also been used with modest success in patients with catastrophic antiphospholipid syndrome (APS).

## Surgery
Surgical intervention is not recommended for the management of antiphospholipid syndrome. However, IVC filter is used for the management of recurrent DVT.

## Prevention
The primary prevention of antiphospholipid syndrome is anticoagulation with low-dose aspirin or warfarin in patients with risk factors for arterial and venous thrombosis, daily low dose of aspirin for primary thrombosis prevention in asymptomatic individuals with persistent antiphospholipid antibodies, minimizing the contribution of reversible risk factors for recurrent thrombosis and use of statins in patients with hyperlipidemia.