Often, symptoms of antiphospholipid syndrome relate to the presence of blood clots. But blood clots often have no symptoms. Other times, they can trigger conditions that have separate symptoms.

Antiphospholipid syndrome (APS) happens when your immune system makes antibodies that mistakenly attack your body’s tissues and organs.

APS is also known as Hughes syndrome or sticky blood syndrome. This is because it mainly affects your blood, making it “stickier” than usual. This can cause blood clots, miscarriages, and other serious complications.

APS is an autoimmune disorder, which mainly affects people assigned female at birth. Many people who’ve gone through multiple pregnancy losses later discover that APS is the underlying cause of their condition.

APS is very rare. It affects fewer than 200,000 people in the United States.

Medical emergency

APS can cause blood clots, which can be fatal. Call 911 if you or your loved ones experience one of the following symptoms:

In this article, we will focus on the symptoms of APS, as well as its complications, effects on pregnancy, and other important topics.

Symptoms of APS can be so variable that it’s sometimes hard to trace them back to the underlying condition.

Most often, symptoms relate to the presence of blood clots. But blood clots can often have no symptoms. In other cases, blood clots can trigger certain conditions, each with a separate set of symptoms.

Here, we’ll discuss the most common signs and symptoms of APS.

Deep vein thrombosis

Deep vein thrombosis (DVT) happens when you have blood clots in a deep vein inside your body. They can happen anywhere, but in most cases, they affect your thighs or lower legs.

Symptoms of DVT include:

  • warmth and swelling in the affected area
  • severe, sometimes cramping pain
  • skin discoloration
  • weakness in the affected limb

High blood pressure

High blood pressure is also known as hypertension. It’s common in people with APS, although doctors don’t entirely understand why.

Hypertension generally doesn’t have any symptoms. Occasionally, people experience the following:

The best way to know if you have hypertension is to get a blood pressure reading. Most doctors perform these at every appointment.

Skin issues

Some people with APS develop a rash that looks like marble due to a pattern of differently colored skin patches. This condition is called livedo reticularis, or mottled skin. It happens due to poor blood circulation caused by blood clots.

You can also develop skin sores, or ulcers, due to APS. In severe cases, lack of blood circulation can cause gangrene (dead tissue) in your limbs.

Superficial thrombophlebitis

Superficial thrombophlebitis happens when you have a blood clot just under your skin. It can occur anywhere on your body but usually affects the lower legs.

The symptoms are similar to DVT but usually less severe. They include swelling, warmth, and tenderness in the affected vein.

Low platelet count

APS can make your blood low on platelets, medically known as thrombocytopenia. In healthy people, platelets clump together to stop you from bleeding out when you have a cut.

If you bruise easily, see a field of tiny, pinprick sized blood spots on your skin (petechiae), or have prolonged bleeding episodes, you may have thrombocytopenia.


People with APS can also develop a special type of anemia, called autoimmune hemolytic anemia (AHA). It makes your immune system mistakenly destroy your own red blood cells.

Not everyone with AHA has symptoms, but you may have pale skin and feel excessively tired. Many people find out that they have anemia through routine blood tests ordered by their primary care doctor.

Other symptoms

Although less common, some people with APS have symptoms that usually happen in multiple sclerosis. These include:

Researchers don’t yet know why these symptoms happen in APS.

In addition to many conditions that can be triggered by APS, it can also have serious, possibly life threatening complications. Let’s discuss these in more detail.

Medical emergency

Conditions described in this section can be fatal, if not treated promptly. If you notice any of the symptoms discussed below, call 911. Do not drive to the hospital.


People with APS are more prone to developing blood clots. If one of the clots dislodges from its original location, it can move and cut off the blood supply to your brain, causing a stroke.

A mnemonic device to identify the symptoms of stroke is called “F.A.S.T.”:

  • Face: One side droops when smiling.
  • Arms: One arm drifts downward when raising arms.
  • Speech: Your speech is slurry or strange.
  • Time: Call 911 right away.

Transient ischemic attack

Transient ischemic attack (TIA) is also known as a “ministroke.” It has the same cause and symptoms as a stroke, but the blockage is temporary. Because of that, stroke-like symptoms usually resolve within a few hours.

Heart attack

A heart attack happens when a dislodged blood clot cuts off the blood flow to your heart.

Symptoms of a heart attack include:

Pulmonary embolism

Pulmonary embolism (PE) is a blood clot that occurs in the lungs.

Symptoms of PE include the following:

APS can cause complications during pregnancy, for example:

Call 911 if you suspect a stroke, heart attack, or PE in yourself or a loved one.

Speak with your doctor, if you have any other symptoms that can point to APS, for example, repeated miscarriages.

APS is an autoimmune disorder that makes your blood clot easily.

It can cause life threatening heart conditions, such as stroke. It can also trigger repeated miscarriages and other pregnancy complications.

Some people have no symptoms of APS, while others experience multiple health issues. Symptoms are usually related to the presence of blood clots. Call 911 if you suspect a blood clot in yourself or a loved one.