Laboratory diagnosis
The diagnosis of PPP is based on clinical presentation and physical exam. Laboratory testing, such as KOH prep, may assist in ruling out dermatophyte infection; a complete blood count may assist in eliminating a bacterial infection as the cause. Skin biopsy is not necessary unless diagnosis is uncertain or prolonged treatment has not produced a response.
Differential diagnosis
The differential diagnosis of PPP includes skin conditions that involve the palms and/or the soles and may have fungal, allergic, or bacterial origins.
Fungal. Tinea manuum (palms) and tinea pedis (soles) result from dermatophyte infection and manifest with erythema and/or scaling and pruritis. A positive KOH examination can confirm diagnosis. On examination, fungal infections are commonly unilateral and asymmetric.8 Treatment with an antifungal agent should result in resolution of symptoms.
Allergic. Contact with an allergen can result in skin erythema, pruritis, and pain at the exposed area. Contact dermatitis can result from an inflammatory response to an allergen or irritant, and it is often localized and well demarcated. This is an acute condition that resolves over time with antihistamines and avoidance of irritants.
Dyshidrotic eczema results in small, pruritic blisters on the palms and the soles and can be recurrent and related to seasonal allergen exposure. Diagnosis is made from history and physical exam. Treatment often consists of emollients and occasionally topical steroids, depending on the severity.
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