Non-bullous variant of bullous pemphigoid: Role of immunofluorescence in diagnosis

Bullous pemphigoid (BP) is a subepidermal blistering disease of the elderly, presenting as tense bullae with flexural predominance and variable pruritus. Unusual variants include vegetating, localized, childhood, urticarial and nodular types. BP can thus mimic a variety of clinical conditions. Due to the nzonvesicular nature of the disease in these forms, the presence of itching and nonspecific histopathology, these cases present a diagnostic problem. We report a case of bullous pemphigoid with itchy excoriated papular lesions who was diagnosed by immunofluorescence.

A 72-year-old lady presented with itchy, erythematous papules, plaques and excoriations with crusting of 4 years′ duration over the trunk, abdomen and extremities [Figure - 1]. The lesions had started on the upper limb and then progressed to involve the lower limb and the lower abdomen. There was flexural predominance, with sparing of the palms, soles, face and mucosae. Lesions on the extremities showed crusting. She also developed dermatitic changes to a plaster cast that had been applied to a leg 6 weeks earlier.

Differential diagnoses of dermatitis, scabies and dermatitis herpetiformis were considered. A therapeutic trial with antibiotics, anti-scabietics and antihistamines showed only mild and temporary improvement. Histopathology from lesional skin showed features of dermatitis with intraepidermal vesiculation. On direct immunofluorescence, strong IgG and C3 deposits at the dermoepidermal junction were seen. Salt split skin sections showed localizaion of immunoreactants to the roof [Figure - 2]. Thus the diagnosis of bullous pemphigoid was confirmed. The patient was started on topical steroids and dapsone 100 mg daily. Within a month, her itching totally subsided and the lesions healed with residual hyperpigmentation. Subsequently the patient was lost for follow up.

Bullous pemphigoid can present as urticarial papules, plaques and excoriations that can precede the onset of blisters by weeks, months or even longer. Later, blistering may arise on normal skin as well as the sites of previous lesions.[1] These cases are usually associated with peripheral blood eosinophilia.[2] Immunofluorescence of the lesional skin is usually positive in such cases. Unusual forms of pemphigoid are vegetating, nodular, hyperkeratotic, localized, childhood, polymorphic and urticarial.[2],[3] BP can also present as erythematous and eczematous lesions.[4] Clinically it can simulate subacute prurigo,[5] scabies,[6] dermatitis herpetiformis or prurigo nodularis.

This case highlights the need to consider the possibility of bullous pemphigoid when an elderly patient presents with persistent, unexplained, excoriated papules. A high index of suspicion coupled with appropriate investigations like immunofluorescence may be required as histopathology is usually nonspecific. Also, follow up of such cases is important as frank vesicobullous lesions could develop later.[4]