Cardiolipin Antibodies

Cardiolipin antibodies (often shortened to aCL) are a type of autoantibody—an antibody that mistakenly targets your own body instead of outside invaders like viruses or bacteria. In this case, these antibodies attack cardiolipin, a fat molecule found in the membranes of many cells, including the mitochondria, the energy-producing centers of our cells. When these antibodies are present, they can disrupt the body’s normal clotting system and are closely linked to two major autoimmune conditions: systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS).

There are three main types, or isotypes, of cardiolipin antibodies: IgG, IgA, and IgM. Each plays a slightly different role:

• IgG aCL is the most common and is strongly linked to serious complications like blood clots, miscarriages, and low platelet counts.
• IgA aCL is less common but critically important. It can appear even when IgG and IgM are absent and is linked to a high risk of clots and low platelet counts.
• IgM aCL tends to show up alongside the other types and is somewhat less strongly associated with severe complications when it appears alone.

Testing for all three isotypes—IgG, IgA, and IgM—gives a fuller and more accurate picture of a person’s risk. Studies show that adding IgA testing can detect up to 30% more cases that would otherwise be missed by IgG and IgM testing alone.

When cardiolipin antibodies are present, they significantly increase the risk of serious health problems, including:

• Thrombosis: formation of blood clots in veins or arteries, which can cause stroke, heart attack, or deep vein thrombosis (DVT).
• Pregnancy complications: including recurrent miscarriages and fetal loss.
• Thrombocytopenia: a condition of low platelet counts that can lead to easy bruising or excessive bleeding.

Of special note, IgA aCL and IgA anti-β2-glycoprotein I (another related antibody) are particularly predictive of blood clots and pregnancy-related issues. Even if IgG and IgM tests are negative, a positive IgA test can reveal hidden risks.

Testing for cardiolipin antibodies is a crucial part of diagnosing antiphospholipid syndrome (APS), a condition where the immune system triggers abnormal blood clotting. By measuring all three isotypes, doctors can better assess a patient’s risk. For example, a patient with negative IgG and IgM but positive IgA results may still be at significant risk for APS complications.

Even outside of diagnosed autoimmune diseases, high levels of IgG or IgA cardiolipin antibodies have been linked to an increased risk of heart attacks and cardiovascular death. This makes cardiolipin antibody testing valuable not just for diagnosing autoimmune disease but also for identifying hidden vascular risks early.