Causes and symptoms

There are two main types of APS:

• Primary antiphospholipid syndrome – the condition is not linked to any other disease and develops in isolation.
• Secondary antiphospholipid syndrome – the condition develops along with another autoimmune disorder, usually lupus.

The good news is that APS is both potentially preventable and treatable if recognised in time; however, as the condition is relatively new in medical terms, much more research is needed until we can learn more about the causes, effects and treatments. One thing we do know is that early diagnosis of APS is crucial for patients, so APS Support UK aims to raise awareness amongst both the medical profession and the general public to achieve earlier diagnosis and the best treatment for patients.

What causes it?

As of yet, we don’t know why people develop APS, why some patients go on to have blood clots while others don’t, why some women (but not all) have pregnancy problems and why some patients are affected by symptoms more than others – vital research is needed before we can answer these questions.

However, we do know that the root cause is an over-activity of the immune system. Usually, the immune system protects the body against foreign invaders – such as viruses or bacteria – by producing antibodies that destroy these harmful substances.

But sometimes, the body gets confused and, in a case of mistaken identity, it makes antibodies against itself, causing an autoimmune disorder.

In patients with APS, the body produces harmful antibodies called antiphospholipid antibodies (aPL). These are abnormal antibodies which attack proteins that are linked to fats in the body.

The most important of these proteins is called beta-2-glycoprotein1. When aPL stick to this protein, it forms a structure called aPL-beta2-glycoprotein1. This structure becomes attached to fats called phospholipids, a type of phosphorous-containing fat molecule found quite normally throughout the body, particularly in the membranes of blood cells and the walls of blood vessels.

Phospholipids contribute to blood clot formation and play an essential role in maintaining proper blood consistency. Due to the phospholipids being attacked by the antibodies, the blood becomes excessively ‘sticky’, resulting in a higher risk of developing blood clots.

Why is the immune system overactive?

We are not sure why the immune system becomes over-active and is unable to distinguish between foreign invaders and its own body constituents. Still, there is increasing clinical evidence that there is probably a genetic tendency which is triggered in people with the condition.

Some APS patients will have family members who also have the syndrome or have histories of other autoimmune diseases in their families, such as lupus or thyroid disease. As well as lupus, other well-known autoimmune diseases include multiple sclerosis, rheumatoid arthritis, and type 1 diabetes.

What triggers the disease?

Again, at this stage, it is unclear, but a person’s genetic makeup and exposure to certain trigger factors may provide the right environment in which APS can develop. One theory is that viral infections, such as glandular fever and shingles, stress, certain drugs, and other well-known precipitants of thrombosis, such as immobility, dehydration, surgery, the oral contraceptive pill and pregnancy, can act as the trigger for the syndrome.

How common is it?

This is difficult to gauge as the condition is often under-recognised and undiagnosed, and few large-scale epidemiological studies have been conducted to provide prevalence data.

However, evidence from a robust study carried out in 2019: “The Epidemiology of Antiphospholipid Syndrome. A Population‐Based Study“, indicates that the prevalence of APS in the population is 1 in every 2000, which means it can be classified as a rare disease.

As widespread research has yet to be carried out into the symptoms of APS, we can only base our statistics on smaller studies, but a general approximate guide which can be applied to APS is the 1 in 6 rule:

• 1 in 6 young (under 50) strokes
• 1 in 6 young (under 50) DVTs
• 1 in 6 young (under 50) heart attacks
• 1 in 6 recurrent miscarriages

In recent years, there has been a movement towards international collaboration, and researchers have now joined together to create APS ACTION – the Alliance for Clinical Trials and International Networking. The trials and collaboration will hopefully yield concrete statistics and improve treatment options for patients in the future.

APS can affect all age groups, from infancy to old age, but most patients are diagnosed when they are between 20 and 50 years old. It is more common among women – for every two men with APS, seven women are affected.