What is the best approach to diagnose and manage pruritis without a rash on the trunk in an elderly female with a slightly elevated white blood cell (WBC) count and elevated monocytes?

Diagnostic and Management Approach to Pruritus Without Rash in an Elderly Female with Elevated WBC and Monocytes

In an elderly female with pruritus without rash and slightly elevated WBC/monocytes, immediately obtain a comprehensive laboratory panel including complete blood count with differential, ferritin and complete iron studies, liver function tests with total bilirubin and serum bile acids, renal function (creatinine/BUN), and thyroid function tests, as iron deficiency and occult systemic disease (particularly hematologic malignancy) are the most critical diagnoses to exclude. 1, 2

Initial Diagnostic Workup

The British Association of Dermatologists recommends the following initial investigations for all patients with chronic generalized pruritus without rash 1, 2:

• Complete blood count with differential - Essential to evaluate the elevated WBC and monocytes, which may indicate lymphoma, polycythemia vera, or other hematologic disorders 1, 2
• Ferritin levels and complete iron studies (serum iron, TIBC) - Iron deficiency is a common and treatable cause of generalized pruritus in elderly females, with iron replacement leading to complete cessation of pruritus shortly after treatment begins 1, 2
• Liver function tests, total bilirubin, and serum bile acids - Cholestatic liver disease is a major cause of generalized pruritus 1
• Urea, electrolytes, and creatinine - Chronic kidney disease and uremia are well-established causes 1
• Thyroid function tests - Should be checked if clinical features suggest thyroid disease 1

Critical Additional Testing Based on Elevated WBC/Monocytes

Given the elevated WBC and monocytes, additional targeted investigations are warranted 1, 2:

• JAK2 V617F mutation analysis - Consider if polycythemia vera is suspected, particularly if aquagenic pruritus is present 1, 2
• Peripheral blood smear review - To evaluate for lymphocytosis or atypical cells suggesting lymphoma 3
• Chest radiography - Hodgkin lymphoma is the malignancy most strongly associated with pruritus, affecting up to 30% of patients with the disease 3
• HIV and hepatitis serology - Should be considered with appropriate risk history 1
• Skin biopsy - Consider for persistent unexplained pruritus to evaluate for cutaneous lymphoma or small fiber neuropathy 1

Most Likely Differential Diagnoses in This Context

The combination of pruritus without rash plus elevated WBC/monocytes raises specific concerns 1, 2:

1. Hematologic malignancy (Hodgkin lymphoma, polycythemia vera, cutaneous T-cell lymphoma) - The elevated monocytes and WBC make this a priority exclusion 1, 3, 4
2. Iron deficiency anemia - Particularly important in elderly females who may have occult gastrointestinal blood loss or poor dietary intake 1, 2
3. Chronic kidney disease - Uremia causes pruritus and can be associated with mild leukocytosis 1, 4
4. Cholestatic liver disease - Can present with pruritus before jaundice develops 1
5. Drug-induced pruritus - 12.5% of drug reactions present with pruritus without rash; review all medications 1

Immediate Management While Awaiting Workup

Begin symptomatic treatment immediately while diagnostic evaluation proceeds 5, 1:

• Emollients and moisturizers - First-line treatment for all pruritus 1
• Topical anti-itch remedies - Refrigerated menthol and pramoxine for symptomatic relief 5
• Non-sedating antihistamines - Such as loratadine 10 mg daily for symptomatic relief, though less effective for non-histaminergic pruritus 1, 3

Treatment Based on Identified Etiology

Once the underlying cause is identified, treatment should be directed accordingly 1:

• Iron deficiency - Iron replacement therapy leads to complete cessation of pruritus shortly after treatment begins 1, 2
• Cholestatic pruritus - Rifampin 150 mg twice daily as first-line; cholestyramine 9 g daily as second-line 1
• Uremic pruritus - Refer to nephrology for dialysis optimization 1
• Paraneoplastic pruritus - May respond to paroxetine, mirtazapine, granisetron, or aprepitant 2
• Severe refractory pruritus - Consider gabapentin, pregabalin, aprepitant, or dupilumab 5

Critical Pitfalls to Avoid

The most critical pitfall is accepting "normal labs" at face value without verifying that comprehensive iron studies and all recommended screening tests were actually performed 2:

• Many patients with iron deficiency and pruritus have been missed because only ferritin was checked, which appeared falsely normal 2
• Ferritin can be falsely elevated as an acute phase reactant; complete iron studies (serum iron, TIBC, transferrin saturation) are essential 2
• Do not dismiss elevated WBC/monocytes as "slightly elevated" - this warrants thorough hematologic evaluation given the association between pruritus and lymphoproliferative disorders 1, 3

Referral Indications

Refer to appropriate specialists based on findings 1:

• Hematology - If peripheral smear shows abnormalities, JAK2 mutation is positive, or lymphoma is suspected 1
• Dermatology - If diagnosis remains uncertain after initial workup, for consideration of skin biopsy, or if pruritus persists beyond 2 weeks without identified cause 1
• Nephrology - If creatinine is elevated for dialysis optimization 1
• Hepatology - If significant hepatic impairment or persistent elevation of liver enzymes is present 1