What are the possible causes of bilateral palmar and plantar erythema with pruritus, also involving the axillary region?

Bilateral Palmar and Plantar Erythema with Pruritus Involving Axillae

The most likely causes are inverse psoriasis, palmoplantar psoriasis, dyshidrotic eczema, or contact dermatitis, with inverse psoriasis being particularly characteristic given the axillary involvement alongside palmoplantar distribution. 1

Primary Differential Diagnosis

Psoriasis Variants (Most Likely)

Inverse psoriasis characteristically presents with erythematous plaques with minimal scale in skin folds, specifically including axillary, genital, perineal, intergluteal, and inframammary areas. 1 The bilateral palmar and plantar involvement combined with axillary lesions strongly suggests this diagnosis, as psoriasis commonly affects both flexural areas and palmoplantar surfaces simultaneously. 1

• Palmoplantar psoriasis presents as well-demarcated, red plaques with silvery scale and can be severely pruritic despite small body surface area involvement. 1, 2 This variant affects 40% of psoriasis patients and significantly impacts quality of life. 2

• The combination of palmoplantar and inverse patterns is common in psoriatic disease, as psoriasis can involve any skin area including hands, feet, and flexural surfaces. 1

Dyshidrotic Eczema

Dyshidrotic eczema is a common cause of palmar and plantar dermatitis in adults, presenting as recurrent vesicular eruptions that are intensely pruritic with characteristic "tapioca pudding" appearance. 3 However, axillary involvement would be atypical for this diagnosis, making it less likely in this presentation.

Contact Dermatitis

Irritant contact dermatitis can affect palms from frequent hand washing or chemical exposure, presenting with erythema, scaling, and pruritus. 1 Axillary involvement could occur from deodorants or clothing irritants, but bilateral symmetric palmoplantar distribution with axillary involvement is less characteristic.

Critical Life-Threatening Causes to Exclude First

Rocky Mountain Spotted Fever

If fever, headache, or systemic symptoms are present with recent tick exposure, Rocky Mountain spotted fever must be considered immediately, as it presents with maculopapular rash spreading to palms and soles 2-4 days after fever onset, with 5-10% mortality if untreated. 4 Urgent doxycycline treatment is required without waiting for diagnostic confirmation. 4

Drug-Induced Causes

Chemotherapy-induced hand-foot syndrome causes redness, marked discomfort, swelling, and tingling in palms, occurring in 6-60% of patients on capecitabine, 5-FU, doxorubicin, or PEGylated liposomal doxorubicin. 4 Obtain medication history including recent chemotherapy, targeted agents (BRAF inhibitors, multikinase VEGFR inhibitors), or other systemic medications. 4

Less Common but Important Considerations

Palmoplantar Pustulosis

Palmoplantar pustulosis is a chronic pustular dermatitis characterized by vesicles, pustules, erythema, and abnormal desquamation affecting palms and soles. 5 While typically localized to palmoplantar surfaces, it can be associated with psoriasis elsewhere (20% of cases). 5 Axillary involvement would be unusual unless part of generalized pustular psoriasis.

Scabies

Scabies should always be considered with severe pruritus and can present with atypical morphology (scabies surrepticius), including erythematous painful palmar lesions, particularly in elderly or immunocompromised patients. 6 Look for finger web involvement, genital lesions in men, breast involvement in women, and household contacts with similar symptoms. 6

Dermatitis Herpetiformis

Dermatitis herpetiformis can present with discrete reddish-brown spots or small blisters on the flexor surface of fingers and palms, though plantar involvement is less common. 7 This diagnosis requires demonstration of granular IgA deposits on skin biopsy. 7

Diagnostic Approach

History Elements to Obtain

• Presence of fever, headache, malaise, or systemic symptoms (suggests infectious etiology like RMSF) 4
• Recent tick exposure or outdoor activities 4
• Current medications, especially chemotherapy agents 4
• Personal or family history of psoriasis or autoimmune disease 1
• Occupational exposures or new irritants (soaps, chemicals, gloves) 1
• Household contacts with similar symptoms (suggests scabies) 6
• Presence of lesions elsewhere on body (scalp, elbows, knees, genital area) 1

Physical Examination Findings

• Examine for well-demarcated erythematous plaques with silvery scale (psoriasis) versus vesicles (dyshidrotic eczema) versus pustules (palmoplantar pustulosis) 1, 3, 5
• Assess axillary lesions for scale characteristics—minimal scale suggests inverse psoriasis 1
• Check scalp, elbows, knees, presacral region, nails, and genitalia for additional psoriatic lesions 1
• Look for burrows in finger webs, wrists, genitalia (scabies) 6
• Evaluate for nail changes: pitting, onycholysis, subungual hyperkeratosis, oil-drop sign (psoriatic onychodystrophy) 1

Treatment Algorithm

For Suspected Psoriasis (Most Likely Diagnosis)

Initiate high-potency topical corticosteroids as first-line therapy:

• Apply clobetasol propionate 0.05% cream or ointment twice daily to palmoplantar lesions 2
• Use clobetasol solution for any scalp involvement 4
• Apply moderate-potency corticosteroids to axillary areas (avoid high-potency in intertriginous areas due to increased absorption and atrophy risk) 1

If inadequate response after 4 weeks of topical therapy:

• Refer for topical PUVA (psoralen plus UVA) therapy 2-3 sessions weekly, which achieves clearance in 50-67% of hyperkeratotic eczema and is effective for palmoplantar psoriasis 1, 2
• Consider oral acitretin 25 mg daily for severe palmoplantar psoriasis, which demonstrates substantial improvement in scaling, thickness, and erythema within 2 months 4, 2

Adjunctive measures:

• Use "soak and smear" technique: soak hands in plain water for 20 minutes, then apply moisturizer to damp skin to enhance penetration 2
• Apply emollients liberally and frequently to all affected areas 1

For Suspected Contact Dermatitis

• Apply moderate-to-high potency topical corticosteroids 4
• Apply moisturizer after every hand wash using lukewarm water 4
• Identify and eliminate potential irritants or allergens 1

For Confirmed Scabies

• Treat with topical permethrin 5% cream or oral ivermectin, plus systemic antibiotics if secondary bacterial infection present 6
• Treat all household contacts simultaneously 6

Critical Pitfalls to Avoid

• Never dismiss fever with palmar rash as simple dermatitis—Rocky Mountain spotted fever mortality increases dramatically with delayed doxycycline treatment. 4 Do not wait for the classic triad (fever, rash, tick bite) before treating, as only a minority present with all three initially. 4

• Do not underestimate the quality of life impact from palmoplantar involvement—it is disproportionate to small body surface area affected and justifies systemic therapy when topical treatments fail. 1, 2

• Always consider scabies in patients with severe pruritus, particularly in elderly or immunocompromised individuals, as it can present with atypical morphology mimicking other dermatoses. 6

• Obtain complete medication history including over-the-counter products and herbal remedies, as drug-induced causes require immediate discontinuation of the offending agent. 1, 4

• If pregnant patient presents with palmar pruritus, measure serum bile acids to exclude intrahepatic cholestasis of pregnancy, which carries stillbirth risk. 2