Lupus is a chronic autoimmune disease where the body’s immune system attacks its own healthy tissues, leading to inflammation and damage in the joints, skin, kidneys, and blood cells. Platelets are small cell fragments in our blood that form clots to stop or prevent bleeding. A low platelet count is a common complication for those with lupus.
The Autoimmune Attack on Platelets
The primary reason for low platelet counts in lupus is immune thrombocytopenia (ITP). The immune system incorrectly identifies platelets as foreign and produces autoantibodies that attach to their surface, tagging them for destruction. This can be one of the earliest signs of lupus, sometimes appearing months or years before a full diagnosis.
Once tagged by autoantibodies, the spleen recognizes the platelets as abnormal. As blood circulates through the spleen, an organ that filters blood, it removes and destroys these tagged platelets. This accelerated destruction leads to a lower overall count in the bloodstream.
In addition to increased destruction, autoantibodies in lupus may also interfere with the production of new platelets in the bone marrow. While the bone marrow may produce more platelet precursor cells, the final stage of platelet formation can be inhibited. This dual mechanism of enhanced destruction and impaired production contributes to reduced platelet levels.
Recognizing Platelet-Related Issues in Lupus
When platelet counts fall, the body’s ability to form clots is diminished, leading to symptoms related to bleeding. One of the most common signs is petechiae, which are tiny, red or purple dots on the skin caused by minor bleeding from capillaries. These often appear in clusters, especially on the lower legs.
Larger patches of bruising, known as purpura, may also appear without injury, and cuts may bleed longer than usual. Other indicators include:
- Frequent nosebleeds
- Bleeding gums, especially after brushing teeth
- Unusually heavy menstrual flows
- Blood in the urine or stool
Low platelet counts are diagnosed with a routine blood test called a Complete Blood Count (CBC), which measures levels of red cells, white cells, and platelets. A normal platelet count ranges from 150,000 to 450,000 platelets per microliter of blood. Thrombocytopenia is diagnosed when the count drops below 150,000 per microliter.
Managing Low Platelet Counts
Managing low platelet counts in lupus depends on the severity. For mild cases with no bleeding symptoms, a “watchful waiting” approach is often used. This involves regular monitoring of platelet levels through blood tests to detect any significant drop without immediate medical intervention.
When treatment is necessary, the first-line option is corticosteroids, such as prednisone. These anti-inflammatory drugs suppress the overactive immune system, reducing the production of autoantibodies that target platelets. While they can increase platelet counts quickly, long-term use is limited due to potential side effects.
If steroids are ineffective or not tolerated, second-line treatments are considered. These include immunosuppressant drugs like mycophenolate mofetil and azathioprine, which dampen the immune response through different mechanisms. Biologic therapies, such as rituximab, offer another option by depleting the B cells that produce autoantibodies.
In emergencies with severe bleeding, intravenous immunoglobulin (IVIG) can be administered to rapidly increase the platelet count. IVIG contains antibodies from healthy donors that temporarily block the spleen from destroying platelets. For severe and persistent cases, a splenectomy (surgical removal of the spleen) may be performed to stop the primary site of platelet destruction.
Associated Conditions and Other Platelet Abnormalities
Antiphospholipid Syndrome (APS) is an autoimmune disorder that can occur with lupus. APS is characterized by antibodies that increase the risk of blood clots (thrombosis). This creates a complex situation where a person with both conditions has a low platelet count (bleeding risk) and a high risk of developing dangerous clots.
The presence of antiphospholipid antibodies complicates management, as treatment must balance the risk of bleeding with the risk of clotting. Blood-thinning medications may be required to prevent clots, even with a low platelet count. APS is diagnosed through blood tests for specific antibodies and a clinical history of clotting or certain pregnancy complications.
While less common, some people with lupus experience thrombocytosis, an abnormally high platelet count. This is considered a reactive thrombocytosis, meaning it is a response to an underlying process like significant inflammation. In rare cases, persistent thrombocytosis might suggest an issue with the spleen, such as functional asplenia, where it is not working correctly.