Differentials
Tinea manuum/pedis
SIGNS / SYMPTOMS
Tinea may rarely present with vesicles.
Patients with tinea often have prominent scale and may also have maceration, especially between the toes, and thickened toenails (onychomycosis).
INVESTIGATIONS
Potassium hydroxide (KOH) prep will be positive, with fungal hyphae appreciated, in tinea.
Consider sending a skin scraping for fungal culture if further confirmation is desired.
Palmoplantar psoriasis
SIGNS / SYMPTOMS
Pustular palmoplantar psoriasis is characterized by pustules on the palms and soles, as opposed to the vesicles of dyshidrotic dermatitis.
Classic lesions of psoriasis (thick, scaling plaques on the elbows and knees) may be present.
INVESTIGATIONS
Skin biopsy of dyshidrotic dermatitis will reveal spongiotic dermatitis.
Psoriasis will have characteristic findings such as psoriasiform hyperplasia and Munro microabscesses.
Allergic contact dermatitis
SIGNS / SYMPTOMS
History may reveal exacerbating factors in contact allergy. Also, the lesions are more inflammatory than those of dyshidrotic dermatitis.
Allergy to topical corticosteroids can be a particularly vexing problem since the dual competing effects of applying the medication in this situation are decreasing inflammation and propagating the allergic response.
INVESTIGATIONS
Patch testing confirms suspected contact allergy.
Scabies
SIGNS / SYMPTOMS
Erythematous papules, especially in the finger webs on the hand.
Excoriated papules will likely be found elsewhere in scabies infestation, especially the genital region and umbilicus.
Burrows may be seen.
Close contacts of the patient will often have a similar eruption.
INVESTIGATIONS
A visualization of skin scrapings from affected areas using mineral oil, glass slides and light microscopy revealing presence of a mite, scybala, or eggs would distinguish scabies from dyshidrotic dermatitis.
Pemphigus
SIGNS / SYMPTOMS
Pemphigus involves skin other than acral sites and is often characterized by flaccid or ruptured bullae as opposed to tense bullae.
INVESTIGATIONS
Skin biopsy will have positive immunofluorescence and characteristic findings on histopathology.
Bullous pemphigoid
SIGNS / SYMPTOMS
Bullous pemphigoid involves skin other than acral sites and may also present with urticarial lesions.
INVESTIGATIONS
Skin biopsy will have positive immunofluorescence and characteristic findings on histopathology.
Irritant contact dermatitis
SIGNS / SYMPTOMS
Irritant contact dermatitis often presents with burning and pain sensation over itch. Primary lesions can be hyperlinear and scaly. Hands, and particularly the dorsal surface due to reduced skin thickness are more often affected than the feet.
INVESTIGATIONS
A detailed history of possible exposures to irritants will help assess this as a possible differential.
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