What is the best course of treatment for a patient with monocytosis, eosinophilia, normal creatine (creatinine) kinase levels, and mild anemia?

Diagnostic Workup and Treatment Approach

The combination of monocytosis, eosinophilia, and mild anemia requires immediate evaluation for parasitic infections (particularly helminthic), followed by assessment for myelodysplastic syndrome (MDS) or chronic myelomonocytic leukemia (CMML) if infectious causes are excluded.

Initial Diagnostic Priority: Rule Out Parasitic Infection

Travel History Assessment

• Obtain detailed travel history to tropical or subtropical regions, as tissue-invasive helminthic parasites are the primary cause of combined eosinophilia and monocytosis 1, 2
• Specifically inquire about consumption of raw or undercooked meat (pork, wild game), as trichinellosis presents with eosinophilia, elevated creatinine kinase, and myalgia 1, 3
• Note that your patient's low creatinine kinase makes trichinellosis less likely, as this infection typically shows CK elevation of 826 IU/L or higher 3

Parasitic Workup

• Perform concentrated stool microscopy (minimum 3 specimens) for hookworm, strongyloides, and other helminths 1, 2
• Order serology for schistosomiasis, strongyloidiasis, and toxocariasis based on geographic exposure 1, 2
• Consider that eosinophilia >1.5 × 10⁹/L persisting >3 months without organ damage requires hematology referral 2

Empiric Treatment for Parasites (if travel history positive)

• Albendazole 400 mg single dose plus ivermectin 200 μg/kg single dose for asymptomatic eosinophilia in returning travelers 2
• For strongyloidiasis specifically: ivermectin 200 μg/kg daily for 2 days 2
• Recheck eosinophil count 2-4 weeks post-treatment to assess response 2

Secondary Evaluation: Hematologic Malignancy

When to Suspect MDS/CMML

If parasitic workup is negative or eosinophilia persists after appropriate treatment, consider myelodysplastic processes, particularly given the monocytosis 1, 4

Bone Marrow Examination Indications

• Persistent monocytosis with cytopenias suggests CMML or MDS with monocytosis 4
• Absolute monocyte count >1000/μL is required for CMML diagnosis; counts below this with dysplasia suggest MDS with reactive monocytosis 4
• Obtain bone marrow aspirate and biopsy with cytogenetics and molecular testing (including SF3B1, TP53, JAK2 mutations) 1

MDS Classification and Treatment

Lower-Risk MDS (if diagnosed)

• First-line for anemia: Erythropoietin-stimulating agents (ESAs) at 30,000-80,000 units weekly of EPO or 150-300 μg darbepoetin alfa 1
• ESAs most effective when baseline EPO <500 mU/mL and transfusion requirement is absent or limited 1
• Add G-CSF to ESAs if neutropenia is present to improve response rates 1
• Response occurs within 8-12 weeks; median duration approximately 2 years 1

Transfusion Support

• Maintain hemoglobin >10 g/dL with RBC transfusions to optimize quality of life in elderly patients 5
• Transfuse at hemoglobin threshold of 8 g/dL, or 9-10 g/dL if comorbidities or poor functional tolerance present 1, 5
• Restrictive strategy (Hb <7 g/dL) reduces mortality, rebleeding, and infections in stable patients without cardiac disease 6

Iron Overload Monitoring

• Consider iron chelation after 20-60 RBC units or when ferritin >1000-2500 μg/L 5
• Monitor cardiac function periodically, as heart iron overload risk increases after 70-80 RBC units 5

CMML-Specific Considerations

• If absolute monocytosis develops (>1000/μL) with dysplasia, diagnosis shifts from MDS to CMML 4
• Patients with MDS evolving to CMML may have better survival than predicted by initial RAEB diagnosis, suggesting a distinct disease biology 4
• Hypomethylating agents (azacitidine or decitabine) are preferred for symptomatic CMML 1

Management of Concurrent Cytopenias

Thrombocytopenia (if platelets <50,000/mm³)

• Thrombopoietin receptor agonists (romiplostim 500-1000 μg/week) achieve 55% platelet response in lower-risk MDS 1
• Only use if marrow blasts <5% 1

Neutropenia (if <1500/mm³)

• G-CSF improves neutropenia in 60-75% of cases 1
• Add to anti-infective therapy during active infections 1

Critical Pitfalls to Avoid

• Do not assume MDS without excluding parasitic infection first, especially with eosinophilia 1, 2, 7
• Do not overlook that malaria causes monocytosis and mild anemia but typically presents with eosinopenia, not eosinophilia 8
• Do not start ESAs without verifying adequate iron stores (ferritin, transferrin saturation) 5
• Do not delay hematology referral if eosinophilia ≥1.5 × 10⁹/L persists >3 months 2
• Do not use absolute monocyte percentage alone—CMML requires absolute count >1000/μL 4

Monitoring Strategy

• Repeat complete blood count in 2-4 weeks after parasitic treatment to assess response 2
• If no improvement or worsening cytopenias, proceed to bone marrow examination 1
• Serial bone marrow assessments every 6-12 months to monitor for clonal evolution in confirmed MDS 1
• Regular assessment for transfusion dependence and iron overload if chronic transfusions required 5