Scabies masquerading as bullous pemphigoid: scabies surrepticius

Abstract

Scabies, a parasitic infestation caused by the mite Sarcoptes scabiei, is diagnosed by observing either the mite, its ova, or its excrement. The mite tracts, known as burrows and a characteristic presentation of the pruritic condition, are typically found on the web spaces between the fingers. Other cutaneous lesions include excoriated papules, pustules, and vesicles. However, atypical clinical variants of scabies, such as bullous, crusted, hidden, incognito, nodular, and scalp forms of the parasitic infestation, mimic the morphologic features of other non-parasitic dermatoses. A 76-year-old man presented with pruritic blisters and urticarial plaques that demonstrated not only pathology changes, but direct immunofluorescence also showed findings of bullous pemphigoid. His condition improved, but did not resolve, with topical corticosteroid cream for the management of the primary autoimmune blistering disorder. When other family members subsequently developed scabies, the correct diagnosis for his condition, bullous scabies, was established by demonstrating mites, ova, and scybala on a mineral oil preparation from a skin scraping of a newly appearing burrow. Bullous scabies can masquerade not only clinically, but also both pathologically and immunologically as bullous pemphigoid. Scabies serrupticius is introduced as a unifying term to designate all of the non-classic presentations of S. scabiei mite infestation.

Keywords: Norwegian; Sarcoptes scabiei; bullous; crusted; egg; hidden; incognito; masquerade; mimic; mite; nodular; pemphigoid; scabies; scalp; scybala; surrepticius.

Figure 1

Scabies masquerading as bullous pemphigoid. Notes: The chest and abdomen of a 76-year-old man show the new appearance of pruritic pinkish-red dermal plaques. Angiomas, present as dark red nodules, are also numerous.

Figure 2

Bullous scabies mimicking bullous pemphigoid. Notes: A closer view of the scabies lesions presenting as pink-red plaques on the left upper abdomen that mimic the urticarial phase of bullous pemphigoid. Biopsy showed a superficial and deep inflammation containing numerous eosinophils.

Figure 3

Scabies surrepticius masquerading as bullous pemphigoid. Notes: A closer view of the scabies lesion on the right lower abdomen; it presents as a tense blister. Biopsy showed a sub-epidermal blister with eosinophils not only in the papillary dermis beneath the base of the vesicle, but also in the superficial and deeper dermis.