Can markedly elevated platelet count (thrombocytosis) be attributed to systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA), and would it be considered reactive thrombocytosis?

From the Guidelines

Elevated platelet counts (1100 × 10^9/L) associated with systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA) would be classified as reactive thrombocytosis. Reactive thrombocytosis occurs when platelet elevation is secondary to an underlying condition rather than a primary bone marrow disorder. Both SLE and RA are inflammatory autoimmune diseases that can trigger increased platelet production through elevated inflammatory cytokines, particularly interleukin-6 (IL-6), which stimulates thrombopoietin production 1. The management approach should focus on treating the underlying autoimmune condition with appropriate immunosuppressive medications rather than directly targeting the platelet count. As the inflammatory disease activity decreases with treatment, platelet counts typically normalize gradually. It's essential to distinguish this from primary thrombocytosis (as seen in myeloproliferative disorders) since the treatment approaches and complications differ significantly. While reactive thrombocytosis from autoimmune conditions rarely causes thrombotic complications on its own, the combination of inflammation and high platelets may increase cardiovascular risk, so appropriate antiplatelet therapy might be considered in some cases based on individual risk assessment 1. Key considerations in managing SLE-related hematological manifestations include:

• Treatment of significant lupus thrombocytopenia with moderate to high doses of glucocorticoids (GC) in combination with immunosuppressive (IS) agents 1
• Use of intravenous immunoglobulin (IVIG) in the acute phase for cases of inadequate response to high-dose GC or to avoid GC-related infectious complications 1
• Consideration of rituximab (RTX) or cyclophosphamide (CYC) in patients with no response to GC or relapses 1

From the Research

Thrombocytosis in Systemic Lupus Erythematosus and Rheumatoid Arthritis

• Thrombocytosis, or elevated platelet count, is not typically associated with systemic lupus erythematosus (SLE) or rheumatoid arthritis (RA) 2, 3.
• In SLE, thrombocytopenia (low platelet count) is more commonly encountered, and thrombocytosis is rarely reported 2.
• A study found that thrombocytosis in SLE patients was often due to reactive thrombocytosis, which can be caused by iron deficiency anemia, polyarthritis, or digital ischemia and/or cutaneous vasculitis 2.
• Another study suggested that thrombocytosis in SLE patients may be associated with autosplenectomy, a condition where the spleen is damaged or removed 3.
• In RA, thrombocytosis can occur, but it is not as well-studied as in SLE 4.
• A study found that patients with RA had increased circulating platelet-leucocyte complexes and platelet activation, which may contribute to the increased risk of thrombosis in these patients 4.

Reactive Thrombocytosis

• Reactive thrombocytosis is a condition where the platelet count is elevated in response to an underlying condition, such as inflammation, infection, or iron deficiency anemia 2.
• In the context of SLE and RA, reactive thrombocytosis may be caused by the underlying inflammatory process or other related conditions 2, 4.
• A platelet count of 1100 would be considered significantly elevated and may be due to reactive thrombocytosis or another underlying condition 2, 3.

Clinical Implications

• The presence of thrombocytosis in SLE or RA patients should prompt further investigation to determine the underlying cause 2, 3.
• If the thrombocytosis is due to reactive thrombocytosis, treatment of the underlying condition may help to resolve the elevated platelet count 2.
• In some cases, thrombocytosis may be associated with an increased risk of thrombosis, and antiplatelet agents may be considered as part of the treatment plan 4.