INTRODUCTION
Bullous pemphigoid (BP) is one of the most common autoimmune bullous diseases. It typically affects the elderly.1 It is characterized by autoantibodies against the basement membrane zone proteins- BP antigen 1 and BP antigen 2. The disease has variable presentation; the typical one consists of tense bulla on reddish base skin and is associated with pruritus. The diagnosis is based on a characteristic clinical manifestations along with immunohistological and immunological findings. It had been found that the disease is more prevalent among certain HLA class II alleles.2 BP had been described in association with neurological diseases.3,4 In addition, several reports described an association of BP and scabies.5,6 Scabies has several clinical presentations - the classical one consists of burrows, nodules, and crusts. However, the epidemiological and clinical presentation of scabies might resemble BP, thus confusion can occur, as reported in case reports of patients with a clinical picture of BP and evidence of scabies. The possible explanations for the overlap vary from superinfection with Staph Aureus (S. Aerus), id reaction, and secretion of lytic enzymes; However, the relationship between these factors and BP is not well determined.7,8 Another possible explanation lies within the speculated pathomechanism for cases of BP induced by scabies, which suggests that exposure of autoantigens induced by a distribution of the basement membrane at the junction of the epidermis and dermis and may start a cascade that contributes to the development of BP. The process was named epitope spreading phenomenon.9 This study aims to evaluate whether an association between BP and scabies truly exists.
MATERIALS AND METHODS
Emek medical center is a tertiary referral center for dermatological patients in northeastern part of Israel. It covers a population of approximately 1 million people.10 It is the only center with an immune pathology service in the area. This population combines 2 major ethnic groups, Jews and Arabs. About 7 percent of the district population is above 65 years old according to the 2008 census.10 We searched the databases of our local health system for patients with a new diagnosis of BP which are residents of the northeastern district of Israel. The database was searched for a time period between January 1, 2009, to December 31, 2016. For each patient, we randomly assigned 3 control subjects without BP that visited our clinic for reasons other than BP. The
