Excerpt from Protothecosis, Cutaneous

Synonyms, Key Words, and Related Terms: Prototheca, Prototheca wickerhamii, P wickerhamii, Prototheca zopfii, P zopfii, cutaneous protothecosis

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Background: The skin is most commonly involved, resulting from primary inoculation through a wound or abrasion. The infection is usually localized to the site of inoculation; however, in immunocompromised individuals, it can become widespread.

Pathophysiology: Prototheca is an achlorophyllic mutant of the green alga Chlorella. The organism is ubiquitous in the environment, particularly in aqueous locales. Infection usually occurs as a result of inoculation into or beneath the skin with subsequent exposure to contaminated water. Person-to-person transmission does not occur. However, Prototheca has been cultured from under the fingernails and other cutaneous sites in healthy individuals.

While healthy individuals can become infected, the organism has low virulence. Protothecosis infections are more commonly described in patients who are immunosuppressed. In healthy individuals, the infection is localized and curable, but cases of disseminated disease in individuals who are severely immunocompromised can be fatal. Cases of disseminated disease have involved the blood, the peritoneum, the GI tract, the liver, and the meninges. A neutrophilic response appears to be critical in eradicating the infection; however, recent reports in the literature dispute this.

Frequency:

In the US: Protothecosis is a rare infection, with fewer than 100 cases reported since the initial report in 1964. Most cases in the United States are from the Southeast, though cases from virtually all geographic regions have been reported.

Internationally: Protothecosis is a rare infection, but it is seen worldwide, with cases reported in Europe, Asia, Africa, and Central and South America.

Mortality/Morbidity: Patients who are severely immunocompromised can develop disseminated disease, which is often fatal.

Localized infection: In immunocompetent individuals, the infection usually remains confined to the skin at the site of inoculation. Olecranon bursitis can develop from protothecosis.

Systemic infection: Rare cases of systemic infection occur almost exclusively in patients who are severely immunocompromised, as in patients receiving chemotherapy, or immunosuppressed patients, such as those on infliximab. Involvement of the meninges has been reported in a few cases of patients with AIDS.

Race: No racial predilection is noted.

Sex: No sexual predilection is evident.

Age: Protothecosis may occur in persons of any age; however, it is exceedingly rare in the pediatric population.