8 Symptoms of Antiphospholipid Syndrome

2. DVT

Deep vein thrombosis (DVT) is a common symptom of antiphospholipid syndrome. It occurs when a blood clot forms in a deep vein, most often in the leg. This happens because APS makes the blood more likely to clot than normal.

DVT does not always cause clear symptoms. Some people feel only mild discomfort or none at all, which can make the condition difficult to notice without medical testing. Even when symptoms are subtle, the clot can still pose serious risks.

When signs do appear, they often include swelling in one leg. The affected area may feel warm, tender, or painful, especially during standing or walking. Changes in skin color, such as redness or darkening, can also occur.

A major concern with DVT is that part of the clot can break free and travel to the lungs, where it can block blood flow and interfere with breathing. This complication is more likely in people with APS.

3. Stroke

Stroke is a serious symptom of antiphospholipid syndrome. It occurs when a blood clot blocks blood flow to part of the brain. This risk is higher in APS because the blood is more likely to clot than normal, and clots may form in the arteries that supply the brain.

When blood flow is reduced, the brain receives less oxygen. Without enough oxygen, brain cells begin to fail and may become permanently damaged. Stroke related to APS can affect younger adults, not only older individuals.

Some people have no warning before symptoms begin, while others notice sudden changes that worsen within minutes. Common warning signs include sudden weakness on one side of the body, trouble speaking, or facial drooping. Vision may blur or be lost in one or both eyes. Confusion and loss of balance can also occur.

Some people experience a short-lived episode called a mini-stroke. The symptoms are similar to a stroke but resolve within hours. Even when they pass, the risk of a more serious stroke remains. Stroke can lead to lasting difficulties with movement, speech, or memory.

4. Heart Attack

A heart attack can occur in people with antiphospholipid syndrome when a blood clot blocks blood flow to the heart. This risk is higher because APS makes the blood more likely to clot. When a clot blocks a coronary vessel, part of the heart muscle is deprived of oxygen, which can damage heart tissue and trigger sudden symptoms.

Heart attacks linked to APS can occur at a younger age than expected and may develop with few or no warning signs. Typical symptoms include chest pain or pressure that may spread to the arm, neck, jaw, or back. Shortness of breath, extreme fatigue, dizziness, and nausea are also common.

5. Pulmonary Embolism

Pulmonary embolism occurs when a blood clot blocks a blood vessel in the lungs. In people with antiphospholipid syndrome, this risk is higher because the blood is more likely to clot. Most clots begin in a deep vein in the leg and can break loose, traveling through the bloodstream to the lungs.

Once lodged, the clot disrupts blood flow and places strain on the heart and lungs. Smaller clots may cause mild or vague symptoms, while larger clots can block major blood flow and become life-threatening. Common signs include shortness of breath, rapid breathing, and sharp chest pain that worsens with deep breaths.

Some people also experience coughing, lightheadedness, or a racing heartbeat. Less obvious symptoms such as unexplained anxiety, weakness, or extreme fatigue can occur. In some cases, leg pain or swelling appears first, which may point to an earlier clot in the leg.

6. Fatigue

Fatigue is a common symptom of antiphospholipid syndrome and goes beyond ordinary tiredness. It can last all day and often does not improve after a full night of sleep. Many people describe it as a persistent lack of energy rather than simple sleepiness.

Blood clots can disrupt normal blood flow to organs and muscles, which may reduce oxygen delivery and affect energy levels. Ongoing symptoms such as pain, headaches, and sleep problems can further drain the body. Emotional stress from living with a long-term condition can also intensify exhaustion.

This type of fatigue can interfere with focus, memory, and mood. People may struggle to stay alert at work or school and find everyday tasks harder to manage. Some notice heavy limbs, slowed thinking, poor concentration, and the need for frequent breaks. Illness, physical strain, and changes in weather can trigger flare-ups and make symptoms worse.

7. Vision Problems

Vision problems can occur when antiphospholipid syndrome affects blood flow to the eyes or to the parts of the brain responsible for sight. Small clots can reduce oxygen delivery to these areas, leading to sudden or gradual changes in vision. Some people experience blurred vision that comes and goes, while others notice double vision or difficulty focusing.

These changes may affect one or both eyes. Temporary vision loss can also occur, with part or all of vision fading for minutes or hours before returning. These episodes are often linked to short-term changes in circulation rather than permanent eye damage.

Triggers such as fatigue, illness, and cold temperatures can make symptoms more noticeable. Vision changes related to antiphospholipid syndrome can interfere with daily activities like reading, driving, and screen use.

8. Mobility, Speech, and Memory Issues

Antiphospholipid syndrome can affect movement, speech, and thinking when small blood clots reduce blood flow to parts of the brain. This can make everyday tasks feel slower, more difficult, or more effortful than usual. Mobility problems often appear as poor balance or reduced control of the arms or legs.

A person may trip more often, feel unsteady while walking, or notice weakness on one side of the body. Speech changes may include slurred speech, difficulty finding words, or slower speech than usual. Longer pauses during conversation can also occur and may feel frustrating, especially when the change appears suddenly.

A person may struggle to remember recent events, follow simple instructions, or stay focused. Mental fatigue is common, and symptoms often worsen during periods of stress, poor sleep, or physical exhaustion.