Systemic Lupus Erythematosus Does NOT Cause Secondary Thrombocytosis
Systemic lupus erythematosus (SLE) is the answer—it causes thrombocytopenia, not thrombocytosis. 1
Understanding the Mechanism
SLE is fundamentally associated with autoimmune destruction of platelets, leading to thrombocytopenia (low platelet counts), not thrombocytosis (elevated platelet counts). 1 The pathophysiology involves antibody-mediated platelet destruction, making it a cause of secondary immune thrombocytopenia rather than reactive thrombocytosis. 2
Why SLE Causes Thrombocytopenia
- Autoimmune platelet destruction is the primary mechanism, with antibodies targeting platelet surface antigens leading to accelerated clearance. 1, 2
- Thrombocytopenia occurs frequently in SLE patients and is almost invariably autoimmune in nature. 3
- SLE-associated thrombocytopenia may be severe enough to require aggressive treatment including splenectomy in refractory cases. 4, 3
The Rare Exception: Autosplenectomy
- When thrombocytosis does appear in SLE (occurring in only 3.7-5.9% of patients), it is typically transient and reactive to other conditions such as iron deficiency anemia, polyarthritis, or cutaneous vasculitis. 5, 6
- Persistent thrombocytosis in SLE should raise suspicion for functional autosplenectomy, particularly in patients with antiphospholipid antibodies. 5, 6
- Only 0.9-1.4% of SLE patients develop persistent thrombocytosis, and this is due to loss of splenic function (autosplenectomy), not the SLE itself. 5, 6
Why the Other Options DO Cause Thrombocytosis
Rheumatoid Arthritis
- Chronic inflammatory conditions like rheumatoid arthritis cause reactive thrombocytosis through cytokine-mediated stimulation of megakaryocyte production. 7
Splenectomy
- Removal of the spleen eliminates the major site of platelet sequestration and destruction, directly causing thrombocytosis. 7
- Post-splenectomy thrombocytosis is expected and can be marked. 5, 4
Inflammatory Bowel Disease
- Active inflammation triggers reactive thrombocytosis through IL-6 and other inflammatory mediators that stimulate thrombopoietin production. 7
Bleeding
- Acute or chronic blood loss stimulates compensatory megakaryocyte proliferation and platelet production, resulting in reactive thrombocytosis. 7
Critical Clinical Pitfall
Never assume thrombocytosis in an SLE patient represents disease activity—instead, investigate for autosplenectomy by examining peripheral blood smear for Howell-Jolly bodies, spherocytes, and target cells, and consider splenic imaging. 5, 6 The sudden appearance of thrombocytosis or apparent reversal of thrombocytopenia in SLE should prompt evaluation for functional asplenia, especially in patients with antiphospholipid antibodies. 6