A protracted course of cutaneous protothecosis: Overcoming recurrence and treatment challenges

This report describes a case of chronic, recurrent cutaneous and soft tissue infection caused by Prototheca wickerhamii in a 50-year-old male, presenting with recurrent skin ulcers and abscess formation. The patient had a history of grade 3 hypertension and gout, along with a record of irregular glucocorticoid use. The clinical course was protracted, spanning nearly two years and involving three hospital admissions with a complex treatment trajectory. The isolate was identified as P. wickerhamii through mass spectrometry and CYTB sequencing. In vitro susceptibility testing demonstrated that amphotericin B (AMB) exhibited potent activity against the P. wickerhamii isolate. While the initial treatment phase was complicated by early missed diagnosis and poor patient adherence, leading to recurrent relapses, a significant therapeutic response was ultimately achieved by employing a comprehensive strategy combining intravenous administration with intralesional injection of AMB for refractory lesions. This case highlights the importance of broadening the differential diagnosis for chronic, nonhealing ulcers in immunocompromised hosts to include protothecosis. Furthermore, it underscores that management should be guided by antimicrobial susceptibility testing; for refractory localized lesions, aggressive local injection therapy is a viable option, and strict adherence management is crucial to minimize the risk of recurrence.