# A case report of multicentric reticulohistiocytosis with atypical cutaneous presentation

## TL;DR

This case report describes an unusual presentation of multicentric reticulohistiocytosis in an elderly man with joint pain followed by large skin nodules.

## Contribution

The report highlights an atypical clinical presentation of MRH and emphasizes the importance of accurate diagnosis through histopathology and immunohistochemistry.

## Key findings

- The patient initially presented with polyarticular pain followed by large, isolated skin nodules—an atypical MRH presentation.
- Accurate diagnosis was achieved through skin histopathology and immunohistochemistry.
- Surgical treatment was performed on the patient's skin lesions.

## Abstract

Multicentric reticulohistiocytosis (MRH) is a rare systemic disorder characterized by histiocytic hyperplasia that mainly involves the skin, mucous membranes, and joints. The typical clinical features include papules, nodules, and arthritis. MRH lesions are relatively extensive but small and scattered. Joint inflammation is characterized by diffuse symmetric polyarthritis as the first symptom, which can be severe and disabling due to destructive joint changes. MRH is easily misdiagnosed in clinical practice. Here, we report the case of an elderly male patient who presented with polyarticular pain in the hip and interphalangeal joints as the first manifestation, followed by the development of large, isolated, bulging skin nodules, which are atypical MRH lesions. This is rare in all MRH case reports, and we made the correct diagnosis by combining skin histopathology, immunohistochemistry, and other clinical examinations. We performed surgical treatment on the local skin lesions of this patient. This case suggests that clinicians should actively correlate the condition and accurately diagnose MRH when encountering atypical skin changes or other diseases as the first symptom and explore the mechanisms of MRH and other clinical manifestations.