What is the diagnosis and appropriate treatment for a patient presenting with leukocytosis and eosinophilia?

Evaluation and Management of Leukocytosis with Eosinophilia

Immediate Assessment

Based on this laboratory profile showing mild leukocytosis (WBC 11.87 × 10³/μL) with mild eosinophilia (absolute eosinophil count 0.44 × 10³/μL), the most likely diagnosis is a reactive process—either an allergic/atopic disorder (which accounts for 80% of eosinophilia cases) or a parasitic infection (the second most common cause)—and the priority is obtaining a detailed travel history, medication review, and assessment for allergic conditions before pursuing invasive testing. 1, 2

Interpretation of Laboratory Findings

• The absolute eosinophil count of 0.44 × 10³/μL represents mild eosinophilia (just above the upper limit of 0.40 × 10³/μL), not the marked hypereosinophilia (>1.5 × 10⁹/L or >3 × 10⁹/L) seen in severe parasitic infections or hypereosinophilic syndromes 3, 1
• The total WBC of 11.87 × 10³/μL with neutrophilia (7.43 × 10³/μL) suggests a mild reactive leukocytosis rather than a primary hematologic malignancy 4, 5
• The absence of immature granulocytes (0.03 × 10³/μL, within normal range) and normal platelet count argue against acute leukemia or myeloproliferative disorders 6, 5

Diagnostic Approach

Essential History Elements

Travel and Exposure History:

• Recent travel to tropical or subtropical regions, particularly Africa (schistosomiasis, filariasis), Asia (strongyloidiasis, ascariasis), or South America 6, 1
• Fresh water exposure in endemic areas (schistosomiasis) 6
• Contact with soil or pets, especially puppies (toxocariasis, hookworm) 1, 7
• Time elapsed since potential exposure is critical—serological tests may not become positive until 4-12 weeks after helminth infection 1, 2

Medication Review:

• NSAIDs, beta-lactam antibiotics, nitrofurantoin can cause drug-induced eosinophilia 1
• Corticosteroids, lithium, and beta-agonists can cause leukocytosis without eosinophilia 5

Allergic/Atopic Symptoms:

• Asthma, atopic dermatitis, food allergies, or allergic rhinitis (80% of eosinophilia cases) 1, 2

Symptom Assessment for Organ Involvement

Respiratory symptoms:

• Fever, dry cough, wheeze, breathlessness, and lower limb pain suggest Tropical Pulmonary Eosinophilia (TPE), though this typically presents with eosinophil counts >3 × 10⁹/L 3

Gastrointestinal symptoms:

• Diarrhea, abdominal pain, weight loss suggest intestinal helminth infections (Strongyloides, Ascaris, Trichuris, hookworm) 6, 1, 8

Constitutional symptoms:

• Fever, weight loss, bruising, or fatigue raise concern for hematologic malignancy 4, 5

Initial Diagnostic Testing

First-Line Investigations

Stool Studies:

• Three concentrated stool samples for ova and parasites (low sensitivity for Strongyloides) 6
• Fecal PCR for helminths if available (more sensitive than microscopy) 6
• Strongyloides stool culture at specialist laboratories 6

Serological Testing:

• Helminth serology panel (Strongyloides, Schistosoma, Toxocara, filaria) 6, 3, 1
• Critical caveat: Serology may be negative in early infection (<4-12 weeks) and can show cross-reactivity between different helminths 1, 2
• IgE levels—markedly elevated IgE (not just mildly elevated) is pathognomonic for TPE when combined with clinical triad 3

Additional Testing Based on Travel History:

• Schistosomiasis serology if fresh water exposure in Africa 6
• Filaria serology if travel to West Africa or Asia-Pacific 6, 3

Peripheral Blood Smear Review

• Assess for toxic granulations, left shift, or atypical cells that might suggest infection versus malignancy 4
• Look for uniformity of white blood cells—abnormal or immature forms suggest primary bone marrow disorder 4, 5

Treatment Approach

For Mild Eosinophilia Without Organ Damage

Observation and Repeat Testing:

• Since this represents mild eosinophilia without evidence of end-organ damage, urgent treatment is not required unless specific parasitic infection is confirmed 3, 2
• Repeat CBC in 2-4 weeks to assess for progression 4
• If eosinophilia persists or worsens, proceed with comprehensive parasitic workup 1

If Parasitic Infection Confirmed

Strongyloidiasis (most critical to identify):

• Ivermectin 200 μg/kg PO as single dose 6
• Must treat even if asymptomatic due to risk of fatal hyperinfection syndrome in future immunosuppression 2

Ascariasis:

• Albendazole 400 mg PO single dose OR mebendazole 500 mg PO single dose OR ivermectin 200 μg/kg PO single dose 6

Schistosomiasis:

• Praziquantel 40 mg/kg PO single dose for S. mansoni 6
• Praziquantel 60 mg/kg PO in two divided doses for S. japonicum/S. mekongi 6

Tropical Pulmonary Eosinophilia (if suspected):

• Before starting diethylcarbamazine (DEC), MUST exclude onchocerciasis with skin snips to prevent blindness 3
• DEC: Start 50 mg day 1, increase to 200 mg three times daily by day 4, continue for 3 weeks total 3
• Alternative: Ivermectin plus albendazole in onchocerciasis-endemic areas 3
• Must exclude Strongyloides before starting steroids if considering treatment for pulmonary fibrosis 3

Empirical Treatment Consideration

• In patients with high-risk travel history and compatible symptoms, empirical anti-helminthic treatment may be appropriate while awaiting serological results, particularly to prevent complications like Trichuris dysentery syndrome 8
• Consider albendazole 400 mg PO daily for 3 days as broad-spectrum empirical therapy for intestinal helminths 6

Red Flags Requiring Urgent Hematology Referral

Refer immediately if:

• WBC >100,000/mm³ (medical emergency due to risk of brain infarction and hemorrhage) 5
• Concurrent unexplained anemia or thrombocytopenia suggesting bone marrow disorder 4, 5
• Fever, weight loss, bruising, hepatosplenomegaly, or lymphadenopathy suggesting malignancy 4, 5
• Persistent high-grade eosinophilia (>1.5 × 10⁹/L) with evidence of end-organ damage (cardiac, pulmonary, neurologic, or skin involvement) 1, 2

Common Pitfalls to Avoid

• Do not dismiss mild eosinophilia—Strongyloides can persist lifelong with only mild eosinophilia and cause fatal hyperinfection decades later 2
• Do not start corticosteroids for presumed allergic disease without excluding Strongyloides first 3
• Do not use praziquantel for T. solium without excluding neurocysticercosis 6
• Do not rely on single stool sample—sensitivity is low; obtain three samples and consider fecal PCR 6
• Do not assume negative serology rules out recent helminth infection—may take 4-12 weeks to become positive 1, 2
• Do not attribute leukocytosis solely to stress or medications without excluding infection and parasitic causes first 4, 5