Normocytic Normochromic Anemia
Plasma cell dyscrasia causes normocytic, normochromic anemia—the type of anemia where red blood cells are normal in size and hemoglobin content but reduced in number. 1
Mechanism and Characteristics
Normocytic, normochromic anemia is the hallmark presentation in multiple myeloma and other plasma cell dyscrasias, defined as hemoglobin ≥2 g/dL below the lower limit of normal or hemoglobin <10 g/dL with normal mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC). 1
The anemia results from multiple mechanisms including bone marrow infiltration by clonal plasma cells (≥10% required for symptomatic myeloma diagnosis), cytokine-mediated suppression of erythropoiesis, and renal insufficiency affecting erythropoietin production. 1
Plasma cell dyscrasias encompass multiple myeloma, Waldenström's macroglobulinemia, AL amyloidosis, POEMS syndrome, and plasma cell leukemia—all of which can present with this anemia pattern. 1, 2
Differential Considerations
Iron deficiency anemia can coexist with plasma cell dyscrasia as a separate entity, particularly in chronic kidney disease associated with myeloma, where functional iron deficiency compounds the normocytic anemia from the malignancy itself. 1
When plasma cell dyscrasia patients develop microcytic anemia (low MCV), investigate for concurrent iron deficiency from gastrointestinal blood loss, reduced absorption, or dialysis-related losses rather than attributing it solely to the dyscrasia. 1
Hemolysis and erythrophagocytosis represent additional mechanisms contributing to anemia in plasma cell dyscrasias beyond simple marrow replacement. 1
Diagnostic Approach
Confirm the normocytic pattern with complete blood count showing normal MCV (80-100 fL) and evaluate peripheral smear for rouleaux formation (red cell stacking) and circulating plasma cells, which are characteristic findings. 1
Bone marrow aspiration and biopsy demonstrating ≥10% clonal plasma cells establishes the diagnosis of symptomatic myeloma when combined with end-organ damage including anemia. 1
Serum protein electrophoresis, immunofixation, and serum free light chain assay are mandatory to identify and quantify the monoclonal protein, though 1-2% of cases are nonsecretory. 1
Clinical Pitfalls
Do not assume all anemia in plasma cell dyscrasia is disease-related—systematically exclude gastrointestinal bleeding, hemolysis, renal disease, and nutritional deficiencies (B12, folate, iron) before attributing anemia solely to the malignancy. 1
Ferritin interpretation is unreliable in plasma cell dyscrasias due to chronic inflammation elevating levels; transferrin saturation ≤20% with ferritin ≤100 μg/L better defines true iron deficiency in this population. 1
The anemia of chronic disease pattern (normocytic, normochromic with low serum iron, low transferrin, normal-to-high ferritin) frequently overlaps with plasma cell dyscrasia anemia, making distinction challenging. 3