# Unusual Presentation of an Orphan Syndrome Masquerading as Castleman Disease in a Young Adult: Diagnostic Challenges and Clinical Implications: A Case Report

## TL;DR

A rare IgG4-related disease was misdiagnosed as Castleman disease in a young man, highlighting the need for careful evaluation and awareness of this condition.

## Contribution

This case report highlights the diagnostic challenges of IgG4-related disease and its resemblance to Castleman disease.

## Key findings

- The patient's condition was initially misdiagnosed as an infectious granulomatous disease.
- Histopathology confirmed the diagnosis of IgG4-related disease with Castleman disease-like features.
- The case emphasizes the importance of timely follow-up and histological evaluation for accurate diagnosis.

## Abstract

IgG4‐related disease (IgG4‐RD) is a rare and diagnostically challenging fibroinflammatory condition characterized by diverse clinical presentations. We present the case of a 33‐year‐old male with a progressively enlarging right groin swelling over 6 months. A similar episode occurred 4 years prior in Nepal, with an inconclusive biopsy. Initial investigations pointed to chronic subcutaneous infectious granulomatous disease with lymphadenopathy. Following multiple missed appointments, the patient underwent excision of a soft tissue mass and lymph nodes. Histopathology revealed features consistent with IgG4‐RD, including follicular hyperplasia and a Castleman disease‐like pattern, negative for malignancy. This case underscores the diagnostic challenges of IgG4‐RD and the importance of considering it in the differential diagnosis of chronic lymphadenopathy. Timely follow‐up, histological evaluation, and awareness of IgG4‐RD diagnostic criteria are crucial for proper management and avoiding delayed treatment.