A Rare Case of Pyoderma Gangrenosum Pointing to Waldenström Macroglobulinemia.

Background: Pyoderma gangrenosum (PG) is a rare, noninfectious, truly nongangrenous, autoinflammatory condition marked by neutrophilic dermatosis. It is characterized by the rapid onset of painful, full-thickness, ulcerative skin lesions with distinctive violaceous and undermined borders. PG is commonly associated with autoimmune and hematologic disorders, namely, inflammatory bowel disease (IBD) and monoclonal gammopathy of undetermined significance (MGUS). However, it has less commonly been reported in association with lymphoplasmacytic lymphoma (LPL) and rarely with its subtype, Waldenström macroglobulinemia (WM). Case Presentation: This case unfolds the story of a 72-year-old female patient with a complex medical and primarily cutaneous oncological history, who initially developed painful lesions on her shins suspected to be PG with a superimposed infection. During extensive infectious, rheumatologic, and oncologic workup revealing an IgM monoclonal gammopathy and antibiotic-resistant infections, her condition quickly deteriorated with altered mental status and eventual cardiopulmonary arrest 2 months after the initial PG diagnosis. Conclusion: This case highlights the importance of close follow-up after PG identification for unusual underlying malignancies and suggests that even an indolent malignancy like WM can contribute to aggressive clinical decline in this setting.