Case Report: Olecranon Bursitis due to Prototheca wickerhamii in an Immunocompromised Patient.

Human protothecosis is a rare algal infection caused by Prototheca; it is a ubiquitous achlorophyllic alga, which rarely causes human disease. Currently, the pathogenesis remains unclear and no treatment options have been elucidated. We present a case of olecranon bursitis caused by Prototheca wickerhamii in an immunocompromised patient. A 45-year-old man presented with left elbow pain after scraping his elbow on a tree. He reported significant pain and swelling of the elbow after injury, which resolved without intervention. He was diagnosed with HIV/AIDS infection and started on antiretroviral therapy. Afterward, he experienced recurrent elbow swelling and pain; an incision and drainage was performed and cultures demonstrated P. wickerhamii. Unsuccessful treatment with oral voriconazole led to an attempt at therapy with parental amphotericin and oral doxycycline; however the patient left against medical advice. He presented to our facility and both parental amphotericin and doxycycline were initiated with planned outpatient bursectomy. He clinically improved on that regimen but left against medical advice before completing his recommended course of IV amphotericin and oral doxycycline. Patients diagnosed with disseminated protothecosis can have a mortality rate upward of 67%. Given the rarity of this pathogen, no official treatment guidelines exist and there are few studies analyzing the antimicrobial susceptibility of Prototheca. Management is challenging because of slow-growing nature of the algae, paucity of research studies, and limited susceptibility of this pathogen. This case adds to the limited body of literature by demonstrating the clinical presentation of protothecosis and highlighting the pathology and current treatment options.