Question:

A 73-year old lady presented with a one week history of multiple itchy, large and tense blisters on her trunk and limbs. There was no recent change in medication. On examination there was no mucosal or genital involvement. Rubbing of the normal skin did not produce new skin lesions. An incisional skin biopsy was performed on one such skin lesion.

Answer: C. Bullous pemphigoid

Bullous pemphigoid is an autoimmune disease seen predominantly in middle aged to elderly patients. It presents as large tense blisters on erythematous urticarial areas, especially on flexural aspects of limbs. The blisters may become haemorrhagic. When widespread they involve the trunk, especially the lower abdomen, groin and axilla. The face and scalp are not usually affected. Mucosal involvement is uncommon. Rubbing of the normal skin does not produce new skin lesion, hence Nikolsky's sign is negative. Skin biopsy shows the blister below the epidermis with neutrophil and eosinophilic infiltrate within the blister and underlying dermis. Direct immuno-fluorescence of peri-lesional skin shows a linear band of C3 and/or IgG deposit at the dermal-epidermal junction. Indirect immuno-fluorescence may show circulating auto-antibodies that binds to dermo-epidermal junction at the roof of salt split skin.

Pemphigus vulgaris presents with lesions on head, neck, trunk, but tends to spare extremities. The blisters are thin-walled, flaccid and rupture easily to form tender erosions. Nikolsky's sign is positive and oral mucosal involvement is common. Skin biopsy findings and direct immuno-fluorescence staining pattern are distinct from that of bullous pemphigoid. Herpes zoster gives rise to tender vesicles and erosions, located asymmetrically over a dermatomal distribution.