What are the differential diagnoses for a 79-year-old woman with a three-day history of isolated palm pruritus and no known allergy history?

Differential Diagnosis: Isolated Palm Pruritus in a 79-Year-Old Woman

The most likely diagnoses in this elderly patient with isolated palm itching are asteatotic eczema (xerosis), drug-induced pruritus, iron deficiency anemia, or early dyshidrotic eczema, with systemic causes requiring exclusion through targeted laboratory testing.

Primary Dermatologic Causes

Asteatotic Eczema (Most Common in Elderly)

• Xerosis and asteatotic eczema are the most common causes of itching in elderly patients over 65 years, often presenting with minimal visible changes initially 1
• The palms can be affected as part of generalized xerosis, particularly in elderly patients with impaired skin barrier function 1
• Look for subtle scaling, fine cracking ("eczema craquelé"), or minimal erythema that may be easily missed 1

Dyshidrotic Eczema (Pompholyx)

• Presents with ferocious pruritus on the sides of fingers and palms, often before visible vesicles appear 2
• Vesicles may be deeply embedded under thick stratum corneum and difficult to visualize initially 2, 3
• Can occur in patients with atopy, sweat gland disorders, or metal allergies 3
• The pruritus phase may precede visible vesiculation by days 2

Contact Dermatitis

• Consider new exposures to soaps, detergents, or topical products 1
• Metal allergy (nickel, cobalt) can trigger palmar dermatitis even without obvious contact 3

Systemic Causes (Critical to Exclude)

Iron Deficiency Anemia

• Iron deficiency accounts for approximately 25% of generalized pruritus cases in elderly patients and can present with localized symptoms 1, 4
• Symptoms typically resolve within days of iron replacement therapy 4
• Order complete blood count with comprehensive iron studies (serum iron, ferritin, transferrin saturation) immediately 1, 4

Drug-Induced Pruritus

• Approximately 12.5% of drug reactions present with pruritus without visible rash 1, 5
• In patients ≥80 years, common culprits include opioids (tramadol), SSRIs (sertraline), atypical antidepressants (trazodone, mirtazapine), and inhaled corticosteroids 1
• Thiazide diuretics and calcium channel blockers are known to cause pruritus in elderly patients 6
• Perform comprehensive medication review including all over-the-counter drugs and herbal supplements 1, 4

Cholestatic Liver Disease

• Cholestatic conditions characteristically cause pruritus predominantly affecting palms and soles, worse at night 7, 4
• May present without jaundice or visible rash initially 7
• Order liver function tests, total bilirubin, and serum bile acids 4

Chronic Kidney Disease

• Uremic pruritus is common in chronic kidney disease and can be localized initially 4
• Order renal panel (urea, electrolytes, creatinine) 1, 4

Hematologic Disorders

• Polycythemia vera can present with pruritus (often aquagenic, but not exclusively) 4
• Early lymphoma may manifest as isolated pruritus 4
• Complete blood count with differential screens for these conditions 4

Less Common but Important Considerations

Infectious Causes

• Scabies can cause severe pruritus with minimal skin findings, especially in immunocompromised elderly patients 4
• Look carefully for burrows between fingers, though these may be subtle 4
• Consider if there are household contacts with similar symptoms 4

Neuropathic Pruritus

• Small fiber neuropathy can cause localized pruritus in elderly patients 1
• Consider if patient has diabetes or other risk factors for neuropathy 4

Medication Side Effect (Specific)

• Palmoplantar pruritus has been reported as a rare side effect of certain vaccinations 8
• Capecitabine and other chemotherapy agents cause palmoplantar syndrome 9

Immediate Diagnostic Workup

Order the following laboratory tests immediately 1, 4:

• Complete blood count with differential
• Comprehensive iron studies (ferritin, serum iron, transferrin saturation)
• Liver function tests, total bilirubin, serum bile acids
• Renal panel (urea, creatinine, electrolytes)
• Thyroid-stimulating hormone (if clinical features suggest thyroid disease)

Initial Management While Awaiting Results

First-Line Topical Therapy

• Apply high-lipid content emollients at least once daily to entire body, as elderly skin has impaired barrier function 1
• Add moderate-potency topical corticosteroid (hydrocortisone 2.5% or clobetasone butyrate) to palms 3-4 times daily for at least 2 weeks to exclude asteatotic eczema 1
• This approach treats the most common cause while diagnostic workup proceeds 1

Symptomatic Relief

• Prescribe non-sedating antihistamines (fexofenadine 180 mg daily, loratadine 10 mg daily, or cetirizine 10 mg daily) for symptomatic relief 1, 4
• Avoid sedating antihistamines (hydroxyzine, diphenhydramine) due to increased fall risk and potential dementia association in elderly patients 1

Self-Care Advice

• Keep nails short to minimize scratch damage 1
• Use mild soaps with neutral pH and avoid hot water 1
• Wear cotton gloves at night if scratching disrupts sleep 1

Critical Pitfalls to Avoid

• Do not dismiss this as "just dry skin" without excluding systemic causes—20-30% of generalized pruritus in older adults has a significant underlying cause 1
• Do not delay comprehensive medication review—drug-induced pruritus is common and reversible 1, 4
• Do not rely on ferritin alone—obtain comprehensive iron studies to avoid missing iron deficiency 4
• Do not assume antihistamines will control systemic pruritus—they are generally ineffective for underlying organ-specific causes 4
• Do not overlook scabies—it can present with minimal findings in elderly or immunocompromised patients 4

When to Refer or Escalate

• Refer to dermatology if symptoms persist beyond 2 weeks despite topical therapy or if diagnosis remains uncertain 1, 4
• Refer to hepatology if significant hepatic impairment or persistent elevation of liver enzymes is present 4
• Refer to hematology if polycythemia vera or lymphoma is suspected 4
• Consider skin biopsy for persistent unexplained pruritus to evaluate for cutaneous lymphoma or small fiber neuropathy 1, 4