Anti-Cardiolipin Syndrome (APS)

Anti-Cardiolipin Syndrome (APS), also known as antiphospholipid syndrome or Hughes syndrome, is an autoimmune disorder characterized by the presence of antiphospholipid antibodies (aPL) in the blood. These antibodies mistakenly target proteins that bind to phospholipids, which are fatty molecules crucial for blood clotting and cell membrane function. The presence of these antibodies increases the risk of recurrent blood clots (thrombosis) in both arteries and veins, as well as complications during pregnancy, such as recurrent miscarriages. APS can occur on its own (primary APS) or in conjunction with other autoimmune diseases, most commonly systemic lupus erythematosus (SLE).

Types of Anti-Cardiolipin Syndrome

APS is classified based on whether it occurs alone or with other autoimmune conditions.

• Primary Anti-Cardiolipin Syndrome:
  • Occurs when APS develops in the absence of any other underlying autoimmune disease.
  • Patients experience symptoms of blood clotting or pregnancy complications solely due to the antiphospholipid antibodies.
• Secondary Anti-Cardiolipin Syndrome:
  • Occurs when APS develops in individuals who already have another autoimmune disease.
  • Most commonly associated with Systemic Lupus Erythematosus (SLE), but can also be seen with other conditions like Sjögren's syndrome, rheumatoid arthritis, or scleroderma.
• Catastrophic Antiphospholipid Syndrome (CAPS):
  • A rare, life-threatening, and rapidly progressive form of APS.
  • Characterized by widespread formation of blood clots in small and large blood vessels throughout the body, leading to multi-organ failure. It requires urgent and aggressive treatment.

Causes

APS is an autoimmune disorder where the immune system produces abnormal antibodies that mistakenly attack the body's own tissues. The exact reason why these antibodies develop is not fully understood, but it's believed to be a combination of genetic and environmental factors.

• Autoimmune Response:
  • The immune system produces antiphospholipid antibodies (aPL), including anti-cardiolipin antibodies, lupus anticoagulant, and anti-beta2-glycoprotein I antibodies.
  • These antibodies interact with proteins on cell surfaces, particularly those involved in blood clotting, leading to an increased tendency for blood clots to form.
• Genetic Predisposition:
  • While not strictly inherited, there may be a genetic susceptibility, as APS can sometimes run in families. Specific HLA genes are associated with an increased risk.
• Environmental Triggers (Possible):
  • Infections: Certain viral (e.g., HIV, Hepatitis C) or bacterial infections (e.g., syphilis) have been associated with the temporary presence of antiphospholipid antibodies, though these usually do not lead to clinical APS.
  • Medications: Some drugs (e.g., hydralazine, procainamide, chlorpromazine, quinidine) can induce antiphospholipid antibodies, though clinical APS is rare.
  • Other Triggers: Trauma, surgery, and prolonged immobility can increase the risk of clotting in individuals with existing aPL.
• Association with Other Autoimmune Diseases:
  • As mentioned, APS frequently coexists with other autoimmune conditions, suggesting shared underlying mechanisms.

Symptoms

The symptoms of APS are diverse and largely depend on where the blood clots form. Recurrent pregnancy complications are also a hallmark of the syndrome.

• Blood Clots (Thrombosis):
  • Deep Vein Thrombosis (DVT): Blood clots in deep veins, most commonly in the legs, causing pain, swelling, redness, and warmth.
  • Pulmonary Embolism (PE): A blood clot that travels from a DVT to the lungs, causing sudden shortness of breath, chest pain, and rapid heart rate. Life-threatening.
  • Stroke: Blood clots in arteries leading to the brain, causing sudden numbness/weakness on one side of the body, speech difficulty, confusion, or vision problems.
  • Transient Ischemic Attack (TIA - "Mini-stroke"): Temporary stroke-like symptoms.
  • Heart Attack: Blood clots blocking coronary arteries.
  • Kidney Clots: Can lead to kidney failure.
  • Clots in Other Organs: Can affect liver, eyes, adrenal glands, etc.
• Pregnancy Complications:
  • Recurrent Miscarriages: Especially in the second and third trimesters.
  • Stillbirth.
  • Premature Birth.
  • Severe Preeclampsia/Eclampsia: High blood pressure and organ damage during pregnancy.
  • Placental Insufficiency: Poor blood flow to the fetus.
• Other Symptoms:
  • Livedo Reticularis: A purplish, lace-like mottled rash on the skin, often on the legs and arms.
  • Thrombocytopenia: Low platelet count, increasing bruising and bleeding risk (paradoxical given clotting tendency).
  • Heart Valve Disease: Thickening or damage to heart valves (most commonly mitral valve).
  • Neurological Symptoms: Headaches, migraines, cognitive dysfunction (memory problems, confusion), seizures.
  • Leg Ulcers.

Diagnosis

Diagnosing APS involves a combination of clinical criteria (history of clotting events or pregnancy complications) and laboratory confirmation of persistently positive antiphospholipid antibodies. The "Sydney Criteria" are commonly used for diagnosis.

• Clinical Criteria:
  • At least one episode of vascular thrombosis (arterial, venous, or small vessel).
  • At least one pregnancy morbidity (e.g., unexplained fetal death after 10th week, premature birth due to eclampsia/preeclampsia/placental insufficiency before 34th week, or three or more unexplained consecutive miscarriages before 10th week).
• Laboratory Criteria (Blood Tests for Antibodies):
  • Lupus Anticoagulant (LA): A test that prolongs clotting times in lab assays (despite causing clotting in the body).
  • Anti-Cardiolipin Antibodies (aCL): Measured as IgG and/or IgM isotypes.
  • Anti-Beta2-Glycoprotein I Antibodies (aβ2GPI): Measured as IgG and/or IgM isotypes.
  • Important Note: Antibodies must be present on two or more occasions, at least 12 weeks apart, to confirm persistent positivity and rule out temporary antibody presence due to infection or medication.
• Exclusion of Other Causes: It's important to rule out other conditions that could cause similar symptoms (e.g., genetic clotting disorders, other autoimmune diseases).

Treatment

Treatment for APS focuses on preventing blood clots and managing pregnancy complications. It primarily involves lifelong anticoagulant (blood-thinning) medication.

• For Patients with a History of Blood Clots:
  • Anticoagulant Medications (Blood Thinners):
    • Warfarin (Coumadin): The mainstay of treatment. Requires regular blood monitoring (INR) to ensure the blood is thinned to the correct therapeutic range.
    • Direct Oral Anticoagulants (DOACs): (e.g., rivaroxaban, apixaban, dabigatran) May be used in some cases, but warfarin is generally preferred for arterial clots or high-risk cases.
  • Antiplatelet Drugs: Low-dose aspirin may be added or used alone in specific situations (e.g., for primary prevention in asymptomatic carriers with high-risk antibody profiles, or for patients with arterial events).
• For Pregnant Women with APS (to prevent complications):
  • Low-Dose Aspirin: Started early in pregnancy.
  • Heparin (Unfractionated or Low Molecular Weight Heparin - LMWH) Injections: Started early in pregnancy and continued throughout pregnancy and often postpartum. These do not cross the placenta and are safe for the fetus.
  • Warfarin is typically avoided during pregnancy due to teratogenicity (risk of birth defects), especially in the first trimester.
• For Asymptomatic Individuals with Antiphospholipid Antibodies:
  • Treatment may or may not be initiated. Discussion with a specialist is crucial, considering antibody profile, other risk factors, and patient preference. Low-dose aspirin might be considered for those with high-risk antibody profiles.
• Management of Catastrophic APS (CAPS):
  • Requires aggressive, rapid treatment in an intensive care setting.
  • Typically involves a combination of anticoagulants, corticosteroids, plasma exchange, and/or intravenous immunoglobulin (IVIg).
• Lifestyle Modifications and Risk Factor Management:
  • Quit smoking.
  • Maintain a healthy weight.
  • Manage blood pressure and cholesterol.
  • Regular exercise (as advised by a doctor).
  • Avoid prolonged immobility (e.g., during long flights or bed rest).

Long-term management of APS requires ongoing monitoring and close collaboration with specialists, including rheumatologists, hematologists, and high-risk obstetricians for pregnant patients.

Living on Anticoagulation With APS

For most people with antiphospholipid syndrome, the diagnosis translates into one lifelong medication and a set of habits that keep it working. The details of which anticoagulant, how it is monitored, and what interferes with it are where the risk is actually managed.

Why warfarin rather than a newer anticoagulant

Direct oral anticoagulants such as rivaroxaban and apixaban are convenient, but in trials in APS they allowed more clots, particularly arterial clots, than warfarin, and they are now generally avoided in people with a history of arterial events or with all three antibody types positive. Warfarin remains the standard, usually with an INR target of two to three and a higher target after a clot on treatment. A lupus anticoagulant can interfere with some INR methods, so the monitoring laboratory needs to know the diagnosis. The hypercoagulation states page covers how APS compares with inherited clotting disorders such as the factor V Leiden mutation.

Keeping the INR steady

Vitamin K intake does not need to be low, only consistent, so leafy greens are eaten in similar amounts week to week. Antibiotics, antifungals, and many supplements swing the INR, which is rechecked within days of any new prescription. Acetaminophen is the preferred pain reliever; NSAIDs such as ibuprofen add bleeding risk on top of anticoagulation. Alcohol in more than modest amounts destabilizes the INR and is another reason to keep it minimal. Our supplement and prescription interactions article lists the common offenders.

Surgery, travel, and hormones

Warfarin is stopped before most operations and bridged with injectable enoxaparin, because the days off anticoagulation are when APS clots. Long flights and car trips call for movement, hydration, and compression, covered in our blood clots and travel article. Estrogen-containing contraception and menopausal hormone therapy raise clotting risk and are avoided in APS; progestin-only methods are the usual alternative.

Lupus, platelets, and the arteries

When APS accompanies lupus, hydroxychloroquine appears to reduce clotting risk as well as treating the lupus and is usually continued. A low platelet count, or thrombocytopenia, is common in APS and complicates anticoagulation, so it is tracked. Because arterial clots are a feature of the syndrome, blood pressure, cholesterol, diabetes, and smoking are treated more aggressively than the numbers alone would suggest.

What to report the same day

A swollen, painful calf, sudden breathlessness or chest pain, or any stroke symptom, however brief, is evaluated immediately even on treatment; the deep vein thrombosis and pulmonary embolism pages describe the signs. So is unexplained bleeding, black stools, or a fall with a head strike. Infection, surgery, and stopping anticoagulation are the usual triggers of the rare catastrophic form. Our hematology team coordinates INR monitoring and specialist care. NHLBI and MedlinePlus publish patient guidance on the syndrome.

If you have APS and were switched to a newer anticoagulant, or your INR has been outside range more than once recently, schedule a visit.