What is the appropriate management for a patient with elevated monocytes, eosinophils, and impaired renal function?

Management of Elevated Monocytes, Eosinophils, and Mildly Elevated BUN

This patient requires a systematic evaluation for eosinophilia with specific focus on parasitic infections, allergic conditions, and medication review, while the mildly elevated BUN and monocytosis warrant assessment for underlying inflammatory or infectious processes.

Initial Assessment Priority

The most clinically significant finding here is the elevated eosinophils (5.4% relative), which requires calculation of the absolute eosinophil count (AEC) by multiplying the percentage by the total white blood cell count to determine severity 1. Eosinophilia is defined as AEC >500 cells/μL, while hypereosinophilia (≥1500 cells/μL) always warrants extensive workup as it is rarely explained by allergy alone 1.

Critical History Elements

For Eosinophilia Evaluation

• Travel history is paramount: Helminth infections are the most common identifiable cause of eosinophilia in returning travelers (diagnosis rates 19-80%), particularly travel to areas with endemic parasitic infections 2
• Medication review: Drugs are among the most common non-infectious causes in low-endemic areas, including NSAIDs, beta-lactam antibiotics, and nitrofurantoin 2
• Assess for organ involvement: Specifically ask about gastrointestinal symptoms (dysphagia, food impaction), respiratory symptoms, cardiac symptoms, skin lesions, and neurological complaints 3, 1
• Allergic history: Evaluate for allergic rhinitis, atopic dermatitis, and asthma, as 50-80% of patients with eosinophilic conditions have allergic diatheses 4

For Monocytosis and Renal Function

• Assess for systemic vasculitis symptoms: Nasal crusting, epistaxis, chronic sinusitis, scleritis, pulmonary infiltrates, hematuria, and peripheral neuropathy suggest granulomatosis with polyangiitis (GPA) 5
• Review for infectious causes: Chronic infections can cause both monocytosis and eosinophilia 2

Diagnostic Workup Algorithm

First-Line Testing

For eosinophilia:

• Stool examination for ova and parasites (three samples on different days) 2
• Serological tests for helminth infections based on travel history (schistosomiasis, strongyloidiasis, filariasis if endemic area exposure) 2
• Complete blood count with differential to calculate AEC 1

For renal assessment:

• Urinalysis with microscopy looking for hematuria, proteinuria, and casts 5
• Serum creatinine and calculate eGFR (BUN of 22.9 mg/dL is mildly elevated and may indicate early renal involvement) 6
• Inflammatory markers (ESR, CRP) 5

If vasculitis suspected:

• PR3-ANCA (c-ANCA) testing, which is 80-90% sensitive for GPA 5
• Complement levels (C3, C4, CH50) 6

Second-Line Testing (If Initial Workup Unrevealing)

• If gastrointestinal symptoms present: Endoscopy with multiple biopsies (six biopsies from at least two different sites) to evaluate for eosinophilic esophagitis, defined as >15 eosinophils per 0.3 mm² 4
• If hypereosinophilia (≥1500 cells/μL): Bone marrow biopsy to exclude clonal eosinophilia and hematologic malignancies 7
• Genetic testing: Cytogenetic and molecular investigations for PDGFR-alpha and PDGFR-beta mutations if primary eosinophilia suspected, as these predict imatinib response 7
• Imaging: Chest CT if pulmonary symptoms or concern for GPA 5

Treatment Approach

For Parasitic Infections (Most Common Cause)

If travel history to endemic areas with mild eosinophilia and no other obvious cause:

• Empirical treatment with albendazole 400 mg single dose PLUS ivermectin 200 μg/kg single dose (for patients >24 months of age) 2

For specific identified infections:

• Most helminth infections: Albendazole 400 mg single dose 4
• Strongyloidiasis: Ivermectin 200 μg/kg single dose 4

For Eosinophilic Esophagitis (If Diagnosed)

• Topical steroids decrease blood eosinophil counts in 88% of patients 4
• Two-food elimination diet for 8-12 weeks with dietitian support 4
• Histological remission defined as <15 eosinophils per 0.3 mm² 4

For Suspected Vasculitis (GPA)

If ANCA-positive with organ involvement:

• Initial therapy: Glucocorticoids combined with either rituximab or cyclophosphamide 5
• Plasma exchange may be considered for pulmonary hemorrhage or severe renal involvement 5
• Maintenance therapy options: Azathioprine, methotrexate, rituximab, or co-trimoxazole 5

For Hypereosinophilic Syndrome (Diagnosis of Exclusion)

• If imatinib-sensitive mutation present: Imatinib is first-line 7
• If no drug target identified: Prednisone and/or interferon alfa for symptomatic patients 7

Critical Pitfalls to Avoid

• Do not dismiss mild eosinophilia: Even mild persistent eosinophilia can cause end-organ damage if left untreated 2
• Strongyloides requires specific attention: Can persist lifelong and present as hyperinfection syndrome with high mortality in immunocompromised patients 2
• Peripheral eosinophil counts may not correlate with tissue eosinophilia: Endoscopy may be needed even with modest peripheral eosinophilia if gastrointestinal symptoms present 4
• Cardiac involvement can be life-threatening: Severe eosinophilia can cause cardiac damage with conduction abnormalities; obtain EKG if AEC >30,000 cells/μL 8
• Testing for eosinophilia alone is inadequate screening: Many helminth infections do not cause eosinophilia 2

Follow-Up Monitoring

• Repeat eosinophil counts after treatment to assess response 4
• If symptoms recur on treatment, repeat endoscopy for histological assessment 4
• Regular ANCA monitoring if vasculitis diagnosed, though treatment decisions should not be based solely on titers 5
• Monitor renal function closely given elevated BUN, particularly if vasculitis or cast nephropathy suspected 6