# The Pericardium Cells Junctions Are a Target for Autoantibodies of Patients Affected by a Variant of Endemic Pemphigus Foliaceus in El Bagre and Surrounding Municipalities in Colombia, South America

## TL;DR

This study shows that patients with a variant of pemphigus in Colombia produce autoantibodies targeting heart tissue, particularly cell junctions in the pericardium.

## Contribution

The study identifies pericardium cell junctions as a novel target for autoantibodies in a specific variant of pemphigus.

## Key findings

- El Bagre-EPF patient sera showed reactivity with pericardial cell junctions and nerve formations.
- Autoantibodies against specific proteins like MIZAP and desmoplakin were found in patients.
- Controls showed no such reactivity, confirming the specificity of the findings.

## Abstract

Background: Patients suffering from a new variant of endemic pemphigus foliaceus in El Bagre, Colombia, South America (El Bagre-EPF) produce autoantibodies (Abs) to different proteins in the skin (frustre form), as well as to those in other organs (Senear–Usher-like and systemic forms). Here, we hypothesize whether patients’ autoantibodies play a role in triggering epicardium and pericardium autoimmunity and pathogenicity. We based this hypothesis on knowing that these patients frequently show clinical symptoms of the chest and heart, and we hypothesize that the autoantibodies of this disease are the main contributors to the base of the pericardial conditions of these patients. Materials and Methods: A case-control study for testing the sera of patients affected by El Bagre-EPF (n = 45) and matched controls from the endemic area (n = 45) was conducted to evaluate reactivity with the pericardial tissue. Patients’ necropsies were tested by immunohistochemistry (IHC), in El Bagre-EPF patients (n = 7) and matched controls. Results: The sera from most El Bagre-EPF patients displayed polyclonal autoreactivity with both layers of the pericardium, i.e., fibrous pericardium and serous pericardium (mainly to cell junctions and sensory nerve formations), as well as with the neurovascular cell junction branches. Controls were negative (p < 0.1). These reactivities were detected by IIF, CM, and IHC using secondary Abs against total IgG, IgM, Kappa and lambda, C3C of the complement, fibrinogen, and albumin. Furthermore, Abs against MIZAP, ARVCF, desmoplakin I-II, and p0071 colocalized with the Abs of El Bagre-EPF (p < 0.1). Conclusions: Patients affected by El Bagre-EPF produce autoantibodies directed against molecules present in the cell junctions of the pericardium and adnexal structures. Further studies will focus on the clinical significance of these findings.