Management of Elevated RDW in Behçet's Disease

Initial Diagnostic Approach

The European Society of Gastrointestinal Endoscopy recommends checking for iron deficiency first, as this is the most common cause of elevated RDW in patients on chronic immunosuppression, by obtaining serum ferritin, measuring transferrin saturation, and reviewing complete blood count 1
A serum ferritin level <12 μg/dL is diagnostic of iron deficiency, and transferrin saturation <30% supports iron deficiency diagnosis 1
Reviewing complete blood count is crucial, looking specifically for microcytosis, though this may be absent in combined deficiencies 1

The British Society of Gastroenterology recommends monitoring for azathioprine-induced myelosuppression, which is a critical differential, by reviewing recent blood counts and checking for early myelosuppression 2, 3, 4
Dose reduction is recommended if lymphocyte count falls below 0.5 × 10⁹/L, platelet count below 50 × 10⁹/L, or neutrophil count below 1.0 × 10⁹/L 4
Considering TPMT status is essential, as deficiency increases risk of myelosuppressive toxicity 2, 3, 5

If iron deficiency is confirmed, the American Gastroenterological Association recommends investigating the source, initiating oral iron supplementation, and considering gastrointestinal evaluation 1
If combined deficiency is present, replacing both deficiencies concurrently with appropriate supplementation is necessary 1, 5
If azathioprine-induced myelosuppression is diagnosed, reducing azathioprine dose or discontinuing, and considering alternative immunosuppression, is recommended 4, 5

The European League Against Rheumatism recommends maintaining current immunosuppressive regimen unless cytopenias require modification, with azathioprine at 2-3 mg/kg/day and low-dose prednisone (typically 5-10 mg/day) 6
Monitoring every 3 months minimum once stable, with complete blood count, liver function tests, and disease activity assessment, is crucial 4, 7

Azathioprine can cause myelosuppression with lymphopenia occurring in 57% of patients, making interpretation of any lymphocyte-based index potentially confounded by medication effects rather than disease activity 8