# Multiple Myeloma: A Forgotten Imitator of Anti-Neutrophil Cytoplasmic Antibody (ANCA) Vasculitis

## TL;DR

This paper discusses a rare case where multiple myeloma mimicked anti-neutrophil cytoplasmic antibody vasculitis, emphasizing the importance of protein electrophoresis in diagnosis.

## Contribution

The novelty lies in highlighting the rare skin manifestations of multiple myeloma and its diagnostic implications.

## Key findings

- Skin involvement in multiple myeloma is rare, occurring in less than 1% of cases.
- Protein electrophoresis is crucial in differentiating multiple myeloma from AAV.
- Multiple myeloma can present with retiform purpura and peripheral neuropathy.

## Abstract

Leukocytoclastic vasculitis is a neutrophilic angiitis with diverse etiologies, including both inflammatory and neoplastic conditions, such as anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) and multiple myeloma (MM). Skin involvement in MM is rare, occurring in less than 1% of cases. We present a case of a patient with retiform purpura and peripheral neuropathy in the lower limbs, secondary to IgG lambda MM, which mimicked AAV. Skin manifestations in MM can appear as the initial symptom or at any stage of the disease. This case highlights the critical role of protein electrophoresis in the initial evaluation of patients with systemic inflammatory conditions.