Dermatology Online Journal

A dilemma: bullous pemphigoid-like eruption in scabies or scabies-induced bullous pemphigoid
Kamran Balighi MD, Reza Mahmoud Robati MD, Nima Hejazi MD
Dermatology Online Journal 12 (4): 13

Department of Dermatology , Razi Hospital, Tehran University of Medical Sciences, Tehran,Iran. robati@razi.tums.ac.ir

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Abstract

Several diseases may be confused with scabies. Atypical manifestations of scabies have previously been reported, including urticaria, contact dermatitis, and dermatitis herpetiformis. There are also reports of scabies mimicking bullous pemphigoid. Here we report a case of scabies in a patient with manifestation similar to bullous pemphigoid. Direct smear of the bullous lesions was performed and was positive for scabies mites. The skin biopsy specimens submitted for light microscopy and direct immunofluorescence study were considered to be compatible with bullous pemphigoid. The patient treated with single dose oral ivermectin and prednisolone. The pruritus subsided and the eruption improved dramatically in 2 weeks.

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Scabies is a contagious infestation associated with the human mite, Sarcoptes scabiei, which affects all social classes worldwide. The most noticeable symptom of scabies is pruritus, especially at night. The characteristic signs of the disease are classic burrows, pruritic papules, and inflammatory nodules [1]. The lesions of scabies infestation can be similar to many dermatoses such as impetigo, psoriasis, urticaria, contact dermatitis, dermatitis herpetiformis, Darier disease, or insect bite [2]. Interestingly, there are some reports of scabies presenting as bullous pemphigoid-like eruption [3, 4, 5, 6, 7, 8]. We report a case of bullous pemphigoid that seems to be induced by scabies infestation and discuss the dilemma whether this entity is scabies induced bullous pemphigoid or bullous scabies.

Clinical synopsis

A 52-year-old man developed generalized itchy papular eruption especially on the trunk, arms, and thighs 3 months after a trip to the north of the country. There was a similar history of this problem in his five-member family. First, their complaints were diagnosed as scabies and treated by topical medications. However, there was subsequent improvement in other members of his family but not for him. The vesiculobullous lesions involved many areas of his body, especially on the axillae, abdomen, inguinal regions, and proximal and distal parts of the upper and lower extremities (Figs. 1, 2, 3). Some pruritic nodules were present on the glans penis (Fig. 4). The mucous membranes were lesion free. There was no previous history of itching and the patient did not report any skin eruption in recent months.

Figure 1	Figure 2
Figure 1: Multiple bullous lesions on the proximal and distal part of upper limbs Figure 2: Multiple bullae on the lower abdomen, inguinal region and proximal lower limbs

Figure 3	Figure 4
Figure 3: Bullous eruption on the posterior aspect of lower limbs Figure 4: pruritic nodule on the glans of the penis.

We took a smear from one of the vesiculobullous lesion and the mites of scabies were present on the direct examination. Biopsy specimens taken from one of the vesiculobullous lesions revealed subepidermal cleft formation containing eosinophils and neutrophils along with an inflammatory infiltrate composed of lymphocytes, neutrophils and eosinophils in the dermis (Figs. 5, 6). The direct immunofluorescence study on a prelesional biopsy specimen showed linear IgG and C3 depositions in the dermoepidermal junction. The indirect immunofluorescence study was done and reported as negative.

Figure 5	Figure 6
Figure 5: Subepidermal split containing eosinophils and neutrophils along with an inflammatory infiltrate composed of lymphocytes, neutrophils and eosinophils in the dermis (H&E × 40) Figure 6: Subepidermal cleft with few eosinophils and neutrophils. (H&E × 100).

The patient treated with oral ivermectin and subsequently with oral prednisolone (80mg/day). After 2 weeks many of the vesiculobullous lesions resolved and the pruritus disappeared. We followed the patient for about 6 months. The dose of oral prednisolone was tapered according to the patient's improvement. At the end of 6 months our patient was free of all pruritus and skin lesions.

Discussion

There are case reports of scabies with bullous pemphigoid-like eruption along with negative or nonspecific findings in direct immunofluorescence assays in the literature. These reports conclude that scabies manifests with a bullous pemphigoid-like eruption or that there is a bullous subtype of scabies infestation [3, 4, 5, 6, 7, 8]. However, some patients with scabies develop bullae concurrently with, or after, the occurrence of scabetic lesions. Although several immunofluorescence studies reported immunoglobulin (IgM, IgA) and complement deposition (C3) in the basement membrane zone or papillary vessels of bullous lesions in patients with scabies [9, 10, 11], it remains in doubt whether these antibodies are directed to bullous pemphigoid antigens. Konishi et al. [12] showed that two scabetic patients with bullous eruptions had circulating antibodies against bullous pemphigoid antigens as determined by Western blotting analysis. They suggested that at least some of the bullous eruptions occurring in scabetics are true bullous pemphigoid.

Our patient was a middle-aged man with diffuse vesiculobullous lesions and positive direct smear for scabies. The histological assay of the biopsy specimen showed a subepidermal cleft with neutrophilic and eosinophilic infiltration; the direct immunofluorescence revealed linear C3 and IgG depositions at the dermoepidermal junction, suggesting the diagnosis of bullous pemphigoid. Resembling many previous reports, the result of indirect immunofluorescence study was negative. However, our patient responded well to ivermectin and then systemic corticosteroid treatment.

One theory to explain the BP-like eruption in the setting of scabies infestation is that lytic secretions from scabies mites alter the BP antigen-inducing production of anti-basement-membrane-zone antibodies. These antibodies activate complement with subsequent infiltration of inflammatory cells and enzyme release to produce subepidermal split [13].

Alternatively, a mite component may play an antigenic role that cross-reacts with the BP antigen resulting in auto-antibody production [14]. It has been suggested that bullous scabies could develop after long persistency of the parasites leading to a specific immune response with activation of T-helper type-2 cells leading to high levels of the cytokine interleukin 5 and subsequent eosinophilia. Secretion of proteolytic enzymes near the basal membrane zone might explain the development of intra-epidermal, often suprabasal blisters. In a patient with a positive biopsy and immunofluorescence result, the scabies infestation may have triggered a flare of the underlying autoimmune disease [5]. According to the result of histological assays and immunofluorescence studies in patients with scabies and bullous pemphigoid-like rash, it is possible to consider two entities, bullous pemphigoid induced by scabies as a Koebner phenomenon and a bullous subtype of scabies similar to bullous pemphigoid [5]. Therefore, both scabies infestation-inducing bullous pemphigoid and bullous pemphigoid-like scabies should be included in the differential diagnosis of itchy vesicles, tense blisters and erythema, particularly at an early clinical stage.

References

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