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Case Reports

Abstract

A 73-year-old woman presented with an 18-month history of a persistent, tender, erythematous dorsal wrist nodule unresponsive to multiple antibacterial, antifungal, anti-inflammatory, and immunosuppressive therapies. She reported frequent dog bites and possible rose thorn injury. Three separate punch biopsies demonstrated granulomatous inflammation without identifiable organisms on hematoxylin-eosin, periodic acid-Schiff (PAS), or Grocott's methenamine silver (GMS) stains. Fungal cultures from five punch biopsies and one excisional biopsy, as well as three broad-range polymerase chain reaction (PCR) tests, were negative. Slight clinical improvement followed the excisional biopsy. Definitive diagnosis was achieved only when the sixth culture grew Sporothrix schenckii complex. Sporotrichosis, a subcutaneous mycosis acquired through traumatic inoculation, often presents with nodular or ulcerated lesions. Histopathology may show suppurative granulomatous inflammation, but low organism burden limits visualization even with special stains. Culture remains the gold standard; however, prior empiric antifungal therapy may suppress fungal growth, contributing to false-negative results. This case highlights the need for persistent culture attempts when suspicion remains high and demonstrates the potential value—yet variable yield—of ancillary PCR-based assays, which may expedite diagnosis when culture sensitivity is reduced. Heightened awareness of these diagnostic challenges can prevent delays in targeted management.