# Pemphigus Foliaceus Mimicking Erythema Annulare Centrifugum: A Case Report

## TL;DR

A 79-year-old woman's skin condition was initially mistaken for psoriasis but was diagnosed as pemphigus foliaceus after biopsy and testing.

## Contribution

This case report highlights the rare annular and polycyclic morphology of pemphigus foliaceus, expanding diagnostic awareness.

## Key findings

- Skin biopsy showed superficial intraepidermal clefting and acantholytic keratinocytes.
- Direct immunofluorescence revealed IgG and C3 deposition, confirming pemphigus foliaceus.
- Treatment with prednisolone and intravenous immunoglobulin led to improvement.

## Abstract

Pemphigus foliaceus (PF) is an autoimmune blistering disease characterized by superficial, easily ruptured blisters that evolve into scaly erosions. Annular and polycyclic morphologies are uncommon in adults and can complicate diagnosis. Here, we describe the case of a 79-year-old woman with pruritic lesions on the trunk, proximal extremities, and face who had initially been treated for psoriasis. Skin examination revealed multiple erythematous annular and polycyclic plaques with central clearing and fine peripheral scaling, without vesicles or bullae. Skin biopsy findings indicated superficial intraepidermal clefting with acantholytic keratinocytes and only scant eosinophils and neutrophils. Direct immunofluorescence (DIF) demonstrated intercellular deposition of IgG and C3 throughout the epidermis. Serological testing confirmed elevated anti-desmoglein 1 and negative anti-desmoglein 3 antibody levels, establishing PF. Prednisolone with adjunctive intravenous immunoglobulin administration led to gradual improvement. Research concerning pediatric PF and erythema annulare-like acantholytic dermatosis supports the view that annular and polycyclic lesions are morphological variants within the PF spectrum. Timely biopsy, DIF, and serological autoantibody testing are key to establishing a diagnosis.