What is the likely cause and recommended management for a patient with leukocytosis (WBC 12.4 ×10³/µL), anemia (hemoglobin 8.7 g/dL, hematocrit 25.8 %), thrombocytosis (platelets 599 ×10³/µL), neutrophil predominance (66 %) and lymphocyte 17 %?

Likely Diagnosis: Reactive Thrombocytosis and Leukocytosis Secondary to Iron Deficiency Anemia

This patient's laboratory findings—moderate leukocytosis (WBC 12.4), significant anemia (Hgb 8.7 g/dL, Hct 25.8%), and marked thrombocytosis (platelets 599)—most likely represent a reactive process secondary to iron deficiency anemia rather than a primary hematologic malignancy.

Diagnostic Reasoning

The constellation of findings strongly suggests reactive thrombocytosis and leukocytosis due to iron deficiency anemia 1. This presentation is characterized by:

• Severe microcytic anemia (Hgb 8.7 g/dL with low hematocrit)
• Marked thrombocytosis (platelets 599 × 10³/µL)
• Mild leukocytosis (WBC 12.4 × 10³/µL)
• Neutrophil predominance (66%) without significant left shift

While extreme thrombocytosis (>1000 × 10³/µL) and leukocytosis (>35 × 10³/µL) have been reported with iron deficiency 1, this patient's more moderate elevations still fit the pattern.

Critical Distinction from Malignancy

This is NOT consistent with acute leukemia or myeloproliferative neoplasm because:

• WBC count is only mildly elevated (12.4 vs. hyperleukocytosis definition of >100 × 10³/µL) 2
• No extreme leukocytosis (>50 × 10³/µL) that would suggest chronic myeloid leukemia 3
• Platelet count elevation is moderate, not extreme (599 vs. >1000 × 10³/µL typical of essential thrombocythemia) 4, 5
• The lymphocyte percentage (17%) is within normal range, not suggesting lymphoproliferative disorder

Immediate Management Algorithm

Step 1: Confirm Iron Deficiency (Within 24-48 Hours)

Obtain the following laboratory tests 6:

• Complete iron studies: serum iron, total iron-binding capacity (TIBC), ferritin, transferrin saturation
• Peripheral blood smear: assess for microcytosis, hypochromia, target cells, pencil cells
• Reticulocyte count: typically low-normal in iron deficiency
• C-reactive protein: to exclude inflammatory causes of anemia 4

Expected findings in iron deficiency:

• Low serum ferritin (<30 ng/mL, or <100 ng/mL if concurrent inflammation)
• Low serum iron with elevated TIBC
• Low transferrin saturation (<20%)
• Microcytic, hypochromic red cells on smear

Step 2: Identify Source of Iron Loss

Investigate for:

• Gastrointestinal bleeding: stool guaiac testing, consider endoscopy if age >50 or alarm symptoms
• Menstrual blood loss: detailed menstrual history in women of reproductive age
• Dietary insufficiency: nutritional assessment
• Malabsorption: celiac serology if indicated

Step 3: Initiate Iron Replacement

Begin oral iron supplementation immediately once iron deficiency is confirmed:

• Ferrous sulfate 325 mg (65 mg elemental iron) orally 2-3 times daily
• Take on empty stomach with vitamin C to enhance absorption
• Continue for 3-6 months to replete iron stores

Monitor response at 2-4 weeks:

• Reticulocyte count should increase within 7-10 days
• Hemoglobin should increase by 1-2 g/dL within 3-4 weeks
• Thrombocytosis and leukocytosis should normalize within weeks to months 1

Step 4: Reassess if Counts Don't Normalize

If thrombocytosis persists after 8-12 weeks of adequate iron replacement, consider:

• JAK2 V617F mutation testing to exclude essential thrombocythemia 4, 5
• CALR and MPL mutation testing if JAK2 negative 5
• Bone marrow biopsy if mutations positive or clinical suspicion remains high 4

When to Suspect Primary Hematologic Malignancy

Immediate hematology/oncology referral is warranted if 7, 8:

• WBC >50 × 10³/µL (suggests possible chronic myeloid leukemia) 3
• Platelets >1000 × 10³/µL (suggests possible essential thrombocythemia) 4, 5
• Presence of immature cells (blasts, promyelocytes) on peripheral smear
• Splenomegaly on examination
• Constitutional symptoms: fever, night sweats, unintentional weight loss
• Concurrent cytopenias in other cell lines
• Failure of counts to normalize with iron replacement

Common Pitfalls to Avoid

1. Do not assume malignancy based on elevated counts alone in the setting of severe anemia—reactive processes are far more common 7, 8

2. Do not delay iron studies while pursuing extensive hematologic workup if clinical picture suggests iron deficiency

3. Do not transfuse red blood cells routinely unless patient is hemodynamically unstable or symptomatic—this can mask the underlying diagnosis and delay appropriate treatment

4. Do not start cytoreductive therapy (hydroxyurea) for thrombocytosis without confirming a primary myeloproliferative neoplasm—reactive thrombocytosis resolves with treatment of underlying cause 9, 10

5. Do not use aspirin prophylaxis for thrombocytosis in this setting unless there is documented essential thrombocythemia with appropriate risk stratification 5

Expected Clinical Course

With appropriate iron replacement, expect:

• Hemoglobin normalization: 2-3 months
• Platelet count normalization: 4-8 weeks 1
• WBC normalization: 4-8 weeks 1

Failure to normalize warrants hematology referral for evaluation of primary bone marrow disorder 7, 4.