By Gary M. White, MD
Human protothecosis is an algal infection due to environmentally ubiquitous achlorophyllic algae: Prototheca species. Prototheca wickerhamii and Prototheca zopfii are the species reported in human infections, and infection occurs predominantly in the immunocompromised, for whom outcomes are often poor.
Slowly growing skin lesions at the site of previous trauma is typical. Papulonodules and plaques are most common.
Diagnosis is usually made histologically showing floret like sporangia with a prominent cell wall. Prototheca wickerhamii produces a morula form of sporangia with endospores arranged symmetrically giving it a soccer ball appearance.
Treatment can be difficult. An infectious disease expert should be consulted. In the past, Amphotericin B, azoles and various antibiotics have been employed.
A 63-year-old male with two weeks of right lower limb swelling, erythema and ulceration. The patient recalled frequent use of a home hot-tub over the preceding months before presentation. The patient was febrile at 38.5° Celsius. Inspection of the right lower leg revealed a 15 cm region of erythema and warmth with central ulceration and several surrounding dark bullae. Med Mycol Case Rep. 2016 Jun; 12: 21–23.