Case Report: Pyoderma gangrenosum masquerading as skin and soft tissue infection preceding myelodysplastic syndrome.

Pyoderma gangrenosum (PG) is a rare, complex, and severe inflammatory dermatosis categorized under the spectrum of neutrophilic dermatoses (NDs), pathologically characterized by sterile neutrophilic infiltration. It is frequently associated with systemic diseases and typically manifests concurrently with or after their diagnosis. We report a rare PG case of an elderly woman who presented 5 months prior to the onset of hematological malignancy (HM), and this unusual clinical presentation led to a misdiagnosis. The patient was initially suspected of having a lower-extremity skin and soft tissue infection (SSTI). Despite repeated debridement and broad-spectrum antibiotic therapy, her condition deteriorated progressively, eventually necessitating amputation. Negative microbial test results ruled out infection. Subsequently, the development of analogous lesions at the venipuncture sites prompted clinicians to reassess the overall clinical condition. Based on prominent neutrophilic infiltration revealed by skin biopsy pathology and the favorable response to glucocorticoid therapy, the initial lower extremity lesions were retrospectively diagnosed as PG. During the follow-up, the patient was diagnosed with myelodysplastic syndrome and was initiated on corresponding treatment. This unusual case enriches the understanding of the PG-HM association and underscores the importance of clinical vigilance and timely reassessment to optimize prognosis.