Diagnosis: Microcytic Anemia with Elevated RDW – Likely Iron Deficiency or Mixed Anemia
This 33-year-old male has microcytic anemia (MCV 82.5, below normal range of ~85-100) with significantly elevated RDW (21, normal <15), which strongly suggests iron deficiency anemia or a combination of iron deficiency with anemia of chronic disease. 1
Diagnostic Workup
The elevated RDW is a critical finding that indicates a wide variation in red blood cell size, which is highly suggestive of iron deficiency even when other causes of microcytosis are present 1. The minimum essential workup must include:
- Serum ferritin and transferrin saturation (TSAT) – These are the cornerstone tests to differentiate iron deficiency from other causes 1, 2
- Reticulocyte count – To assess bone marrow response; low or "normal" reticulocytes indicate deficiency states rather than hemolysis 1
- C-reactive protein (CRP) – To detect inflammation that would alter ferritin interpretation 1
- Peripheral blood smear – To evaluate red cell morphology and confirm microcytosis/hypochromia 1
Interpretation of Iron Studies
The ferritin threshold depends critically on inflammatory status 1, 2:
- Without inflammation (normal CRP): Ferritin <30 μg/L confirms iron deficiency 1
- With inflammation (elevated CRP): Ferritin up to 100 μg/L may still represent true iron deficiency 1, 2
- TSAT <16% indicates absolute iron deficiency 2
- TSAT <20% with ferritin >100 μg/L suggests anemia of chronic disease 1, 2
The microcytic hypochromic pattern in this patient strongly favors coexisting iron deficiency, as pure inflammatory anemia typically presents as normocytic 2.
Management Plan
If Iron Deficiency is Confirmed (Ferritin <100 μg/L or TSAT <20%)
Start oral iron supplementation with ferrous sulfate 200 mg three times daily for at least 3 months after hemoglobin correction 2. Monitor response at 2-4 weeks; expect hemoglobin increase of at least 2 g/dL within 4 weeks if treatment is effective 1, 2.
If oral iron fails after 2-4 weeks, switch to intravenous iron, particularly if malabsorption is suspected 2. The target is to normalize both hemoglobin levels and iron stores 1.
If Anemia of Chronic Disease is Present
Treat the underlying inflammatory or infectious condition as the primary intervention, as anemia will not resolve without controlling the underlying disease 2. Iron supplementation should still be given if TSAT <20% or ferritin <100 μg/L 1, 2.
Monitoring Schedule
- Recheck CBC, ferritin, and TSAT at 2-4 weeks to assess response 2
- Monitor hemoglobin and red cell indices at 3-month intervals for one year, then annually 2
- An increase in hemoglobin of ≥10 g/L within 2 weeks indicates iron deficiency is contributing 2
Red Flags Requiring Extended Workup
If standard iron studies are unrevealing and anemia persists despite treatment, consider 1, 2:
- Vitamin B12 and folate levels – Though less likely with microcytosis, combined deficiencies can neutralize MCV 1
- Haptoglobin, lactate dehydrogenase, and bilirubin – To exclude hemolysis 1
- Bone marrow examination – If cause remains unclear after extensive workup 1
- Genetic disorders of iron metabolism – Particularly if there is extreme microcytosis, family history of refractory anemia, or iron loading 1, 2
Common Pitfalls to Avoid
Do not assume normocytic anemia based solely on MCV in the low-normal range – This patient's MCV of 82.5 is technically microcytic for an adult male, and the markedly elevated RDW (21) is pathognomonic for iron deficiency 1. When microcytosis and macrocytosis coexist, they can neutralize each other and result in a falsely normal MCV; the high RDW reveals this mixed picture 1.
Do not withhold iron supplementation if ferritin is between 30-100 μg/L in the presence of inflammation – This range likely represents a combination of true iron deficiency and anemia of chronic disease 1, 2.
Do not treat with iron alone if an underlying chronic disease is present – The inflammatory condition must be addressed simultaneously 2.