# Autoimmunity to Collagen XVII (BP180‐Ag2) in Pemphigoid Associated With Parkinson’s Disease

## TL;DR

An 84-year-old Parkinson’s patient developed bullous pemphigoid, with autoimmunity to collagen XVII (BP180-Ag2) possibly linking the two rare conditions.

## Contribution

Identifies a novel autoimmune link between Parkinson’s disease and pemphigoid through reactivity to BP180-Ag2 antigen.

## Key findings

- Patient’s serum and blister fluid showed reactivity to BP180-Ag2 antigen via ELISA.
- Only one of six Parkinson’s control sera reacted to BP180-Ag2.
- Autoantibodies targeted basement membrane and antineuronal antibodies were detected.

## Abstract

The association between Parkinson’s disease and autoimmune disease is rare; in our population, there is 1 case per 10,000 inhabitants. Bullous pemphigoid has a much lower incidence, and consequently, the association of Parkinson’s disease and bullous pemphigoid is rarer. We present the case of an 84‐year‐old patient with a 16‐year history of Parkinson’s disease, treated with rotigotine, levodopa, and carbidopa. The patient spontaneously developed tense blisters that spread to the trunk and extremities within 1 year of the first occurrence of dermatological symptoms. A lesional biopsy revealed a subepidermal blister with inflammatory infiltrates, and immunofluorescent evaluation of the biopsy revealed immune deposits of IgG at the basement membrane. The serum displayed antibasement membrane autoantibodies that reacted with monkey esophagus tissue, and immunofluorescence revealed that the patient was positive for antineuronal antibodies that reacted with mouse brain tissue. The molecular reactivity of the serum and fluid obtained from a bulla was positive for the BP180‐Ag2 antigen, as determined by ELISA. Additionally, six Parkinson’s serum samples without pemphigoid disease were tested as controls, and only one serum sample was reactive to BP180‐Ag2. A critical review of the possible pathogenic mechanisms of this rare association is discussed.