Can Rheumatoid Arthritis (RA) cause an elevated White Blood Cell (WBC) count?

From the Guidelines

Yes, Rheumatoid Arthritis (RA) can cause an elevated white blood cell (WBC) count, as evidenced by the inflammatory nature of the disease, which can lead to increased production of white blood cells in response to active disease flares 1. During these flares, the body's immune response is heightened, triggering the release of more white blood cells into the bloodstream. This elevation typically reflects the ongoing inflammatory process that characterizes RA, where the immune system is actively attacking joint tissues.

The increase in WBCs is often modest, typically in the range of 10,000-15,000 cells per microliter, rather than the dramatic elevations seen in severe infections. However, some studies suggest that leucocytosis, or elevated WBC count, can occur in patients with inflammatory arthritis, including those with conditions similar to RA, such as adult-onset Still's disease (AOSD) and systemic juvenile idiopathic arthritis (sJIA) 1.

Key points to consider include:

• The prevalence of leucocytosis (>10,000/mm³) in patients with sJIA and AOSD was found to be around 79% and 62%, respectively, in one study 1.
• The increase in WBC count can be influenced by disease activity, with more active disease leading to higher WBC counts.
• Medications used to treat RA, such as corticosteroids, can also independently cause WBC elevation, while other treatments like methotrexate, leflunomide, or biologics may suppress WBC counts.
• When evaluating an elevated WBC count in an RA patient, clinicians must consider whether it represents disease activity, medication effects, or possibly an unrelated infection, as RA patients have increased susceptibility to infections due to both the disease itself and immunosuppressive treatments.

Given the most recent and highest quality evidence available, the relationship between RA and elevated WBC count is supported, particularly in the context of active disease flares and the use of certain medications 1.

From the Research

Rheumatoid Arthritis and Elevated White Blood Cell Count

• Rheumatoid Arthritis (RA) can be associated with changes in White Blood Cell (WBC) counts, although the relationship is complex and influenced by various factors including disease activity and treatment [(2,3)].
• Studies have shown that while WBC counts are usually within the normal range or slightly elevated in RA patients 2, leukocytosis (elevated WBC count) can occur in a subset of patients, particularly those with more active arthritis or receiving steroid therapy 3.
• The elevation in WBC count is primarily due to an increase in neutrophils 3, and newly detected leukocytosis in RA should prompt an evaluation for occult infection 3.
• Other studies have focused on specific subsets of immune cells, such as CD4+CD25high T cells, which are enriched in the peripheral blood of RA patients 4, but the suppressive function of these cells may be diminished due to the increased number of activated effector T cells.
• In addition to WBC counts, other platelet indices, such as mean platelet volume (MPV), have been found to reflect disease activity in RA patients 5.
• In rare cases, RA can be associated with reductions in WBC count, as seen in Felty syndrome, a life-threatening complication characterized by neutropenia, anemia, and thrombocytopenia 6.