Introduction
Localized skin infection is common and typically caused due to primary inoculation through abrasion or wound. In immunocompromised people, infection with prototheca can become extensive. There are six species involved in the genus prototheca:
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Prototheca wickerhamii.
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Prototheca zopfii.
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Prototheca blaschkeae.
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Prototheca cutis.
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Prototheca ulema.
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Prototheca stagnora.
The first four species mentioned above cause infections in humans, Prototheca wickerhamii being the most common. However, prototheca infections have also been reported in cats, cattle, and dogs.
What Is the Cause of Protothecosis?
The infection is commonly caused by Prototheca wickerhamii. Less common infections are seen in Prototheca zopfii species. Prototheca is found everywhere in the environment. It can be cultured from various water sources, including lakes, ponds, streams, and tap water. Prototheca species are also found in animal feces, soil, and other sources. This organism is widely present in the environment but does not produce infection in most individuals. Most of the cases reported are in immunocompromised individuals, such as people on long-term immunosuppression for organ transplantation, graft versus host disease, autoimmune disease, radiation therapy, or chemotherapy, HIV (human immunodeficiency virus) and AIDS (acquired immunodeficiency syndrome) infection, diabetes mellitus, Cushing disease, or chronic renal failure.
What Are the Signs and Symptoms of Protothecosis?
The individual may have a history of trauma that is abrasion or cut to the skin and subsequent exposure to contaminated water. Usually, farmers, aquarium staff, anglers, and handlers of raw seafood. The skin is the common site of infection, followed by periarticular bursae, which causes olecranon bursitis. The extremities are commonly involved.
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Affected individuals usually have an isolated ill-defined plaque or nodule.
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Large pustular lesions, eczematous plaques, and cutaneous ulceration are also seen.
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The lesions may be herpetiform, atrophic, verrucous, or hypopigmented.
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Bullous lesions may undergo rupture, drainage, and crusting.
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Lesions have an apple jelly appearance.
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There may be erythema and pain.
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Individuals with olecranon bursitis have swelling, mild erythema, and drainage.
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Meningeal involvement may show signs of nuchal rigidity, headache, and photophobia.
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Initial signs include fever, abdominal pain, skin lesions, headache, and diarrhea.
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There may be algaemia which is the involvement of blood with jaundice, and hepatitis is also seen.
How common is protothecosis?
Frequency:
Protothecosis is rare, and most cases include the skin and nails. Protothecosis cases are reported worldwide. In the United States, cases are commonly from the Southeast region.
Age:
Protothecosis is common in individuals older than 30 years or older adults, although pediatric cases have also been reported.
What Is the Pathophysiology of Protothecosis?
Prototheca is an achlorophyllous variant of green alga chlorella. The organism is commonly found in aqueous environments. Infection occurs by inoculation into the dermis or subcutis by an injury associated with swampy water or contamination. Inoculation can also occur by traumatic exposure with no water exposure. Infection is a post-surgical complication. Person-to-person transmission is less likely. Prototheca has also been found underneath fingernails and other cutaneous sites in healthy individuals. The organism has low virulence in healthy individuals. Many cases reported the infection is common in individuals with hematological malignancy or a history of organ transplantation. Widespread use of immunosuppressive drugs also increases the risk of infection. Immunosuppressants such as topical, oral, or locally injected glucocorticoids are often associated with the onset of protothecosis. The infection is often localized and curable in healthy people but can be fatal in immunocompetent cases. The disseminated disease involves the peritoneum, blood, liver, gastrointestinal tract, and meninges.
What Is the Prognosis for Protothecosis?
Individuals with localized infection or disease have an excellent prognosis and cure. However, the prognosis of individuals with severe disease and immunosuppression is poor.
Localized Infection:
In immunocompetent individuals, the infection remains restricted to the skin at the site of inoculation. Olecranon bursitis can lead to protothecosis. In rare cases, tenosynovitis is observed secondary to protothecosis. Infection of a corneal graft may also be seen. Protothecosis has also been reported in the setting of ustekinumab therapy for psoriasis.
Systemic Infection:
Systemic infections are rarely seen, almost exclusively in individuals who are severely immunocompromised, as in individuals receiving chemotherapy, or immunosuppressed individuals, such as those taking Infliximab. In cases of AIDS (acquired immune deficiency syndrome), meninges are involved.
How Is Protothecosis Investigated?
Laboratory Studies:
A diagnosis is obtained based on findings from either culture or biopsy. As it has been established that protothecosis is common among immunocompromised individuals, an immune status evaluation may be essential in individuals presenting with this disorder.
Other Tests:
Electron microscopy may reveal a double-layered cell wall without chloroplasts. These features help in differentiating prototheca organisms from algae. Commercial systems such as API 20C and VITEK 2 help identify Prototheca species. Newer technologies such as MALDI-TOF MS help in identifying Prototheca wickerhamii species.
What Is the Treatment for Protothecosis?
Medical Care:
Protothecosis can be hard to eradicate. Successful treatment is seen with Ketoconazole, Fluconazole, and Itraconazole. Voriconazole is also effective. In immunocompetent individuals, isolated lesions such as Azoles are surgically removed with antifungal therapy. Dual use of a local thermal application is an adjunct to Azole therapy. Studies conducted reported that itraconazoler day for two months can be useful in some adults.
Surgical Care:
Surgical excision is the treatment for all cases amenable to excision. Debridement for necrotic ulcerative lesions may be warranted. Olecranon bursitis is managed by bursectomy.
What Is the Differential Diagnosis of Protothecosis?
The differential diagnosis includes the following:
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Blastomycosis is similar to pyoderma.
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Deep fungal infection.
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Eczema.
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Chromoblastomycosis.
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Atypical mycobacterial diseases.
Prevention:
Immunocompromised and healthy individuals should avoid swimming or bathing in swampy or stagnant water bodies. In addition, people diagnosed with protothecosis should undergo a medical examination for underlying immunosuppression if a predisposing factor is unknown.
Conclusion:
Protothecosis is an emerging environmental disease with high mortality rates in immunocompromised individuals. In immune deficiency, the destruction of the skin barrier caused by catheter and surgery may be associated with infection. Organ transplantation is a common risk factor, followed by leukemia. Prototheca wickerhamii and Prototheca zopfii are species that often cause disseminated infection.
