Differentials
Herpes simplex
SIGNS / SYMPTOMS
Monomorphic grouped vesicles.
INVESTIGATIONS
Viral polymerase chain reaction (PCR).
Viral direct immunofluorescence swab or viral culture and Tzanck prep when PCR unavailable.
Varicella
SIGNS / SYMPTOMS
Widespread vesicles at different stages.
Oral mucosa may be affected.
INVESTIGATIONS
Viral polymerase chain reaction (PCR).
Viral direct immunofluorescence swab or viral culture and Tzanck prep when PCR unavailable.
Dermatophytosis (Tinea corporis, Tinea capitis)
SIGNS / SYMPTOMS
Peripheral scale.
Central clearing.
Crusting infrequent except in scalp kerion.
Bullous dermatophytosis commonly occurs on the instep of the foot.
INVESTIGATIONS
Microscopy of skin scrapings and fungal culture.
Candida
SIGNS / SYMPTOMS
Satellite lesions.
Affected areas are usually more confluent.
INVESTIGATIONS
Bacteriology swab for culture.
Discoid or contact dermatitis
SIGNS / SYMPTOMS
Pruritus invariably present.
Very fine circular scaling or vesicles.
INVESTIGATIONS
Skin biopsy confirmatory.
Pemphigus vulgaris
SIGNS / SYMPTOMS
Larger superficial blisters may be seen early. Seen more commonly in older patients.
Prominent mucosal involvement.
INVESTIGATIONS
Skin biopsy confirmatory.
Immunofluorescence helpful.
Stevens-Johnson syndrome
SIGNS / SYMPTOMS
Involvement of the conjunctiva.
Patient systemically ill.
INVESTIGATIONS
Skin biopsy confirmatory.
Bullous erythema multiforme
SIGNS / SYMPTOMS
Target lesions with violaceous center.
Patient uncomfortable.
INVESTIGATIONS
Skin biopsy confirmatory.
Dermatitis herpetiformis
SIGNS / SYMPTOMS
Multiple vesicles grouped on the lower back and around the elbows and knees.
Intensely pruritic vesicles.
INVESTIGATIONS
Skin biopsy confirmatory.
Bullous lupus erythematosus
SIGNS / SYMPTOMS
More commonly found on exposed areas of the body.
INVESTIGATIONS
Skin biopsy confirmatory.
Bullous scabies
SIGNS / SYMPTOMS
Dermoscopy showing the classic burrow found particularly on the hands, elbows, and genitals, is diagnostic.
INVESTIGATIONS
Microscopy of skin scrapings taken carefully are diagnostic.
Erysipelas
SIGNS / SYMPTOMS
Sharply demarcated erythematous plaques; typically unilateral and on the face.
Edema and warmth are common features.
INVESTIGATIONS
Clinical diagnosis usually suffices.
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