Algas en la piel...
Adding protothecosis to the protocol

By Warren R. Heymann, MD, FAAD
April 23, 2025
Vol. 7, No. 16
Davies et al. reported the first human infection with a Prototheca alga 60 years ago in a Sierra Leone barefoot rice farmer's foot. Almost 300 cases of human Prototheca infections have been reported since. (1,2) Described in 1894 as a fungus and subsequently reclassified, Prototheca are achlorophyllous saprophytic algae found ubiquitously in soil and water, especially when contaminated by organic waste, as in sewage and ponds. (3) Prototheca infection characteristically presents in three primary forms: cutaneous, olecranon bursitis, and systemic (disseminated) disease. Cutaneous infections commonly arise in immunocompetent patients, while disseminated infections predominantly impact immunocompromised individuals. According to Chen et al., "the prevailing belief is that Prototheca species infect humans either through direct contact with exposed areas or via traumatic inoculation of materials contaminated with the algae." (2) Although there are multiple species of Prototheca, the two main pathogens are Prototheca wickerhamii and Prototheca ciferrii (previously known as P. zopfii genotype 1). (2,3)
Even though patients with cutaneous disease may not be immunosuppressed in the classical sense, mild immune dysregulation may predispose to Prototheca infection. Examples include a 40-year-old man taking methotrexate for reactive arthritis who developed cutaneous protothecosis appearing as a nodule on his finger after washing algae from a freshwater aquarium; a 68-year-old fisherman who practiced canoeing on a dam presented with vesicles at the base of the penis which had evolved over 6 months into an infiltrated and painful erythema throughout the inguinal region. His history of significant obstruction of a prosthesis used to treat an abdominal aortic aneurysm may have caused vascular insufficiency with localized immune dysregulation. (4)

Shakoei et al. state, "Disseminated protothecosis is a rare disease in immunocompromised patients but is generally rarer in immunocompetent hosts. Several underlying disorders include immunocompromised patients, prolonged application of steroids, diabetes mellitus, malignancies, organ transplantation, AIDS, and surgeries." In their review of 54 cases of disseminated protothecosis (including their patient) 39 were due to P. wickerhamii, 12 were due to P. zopfii (22.2%), and three were due to Prototheca spp. More men were affected (37 cases, 68.5%) than women (16 cases, 29.6%). The mean age of patients was 39.53 ± 22.48 years, although the age range was from 1-80 years. (6)
The differential diagnosis of prothecosis includes: a) Subcutaneous fungal infections after primary inoculation (e.g., sporotrichosis, cryptococcosis, chromoblastomycosis); b) Nontuberculous Mycobacteria infections (e.g., Mycobacterium marinum, "the fish tank granuloma"); c) Cutaneous candidiasis; d) Unusual cutaneous infectious bacterial agents — (e.g., Erysipelothrix rhusiopathiae [erysipeloid], Serratia marcescens); e) Cutaneous botryomycosis; f) Donovanosis (granuloma inguinale); and g) Neutrophilic dermatoses — (e.g., Behçet's disease, pyoderma gangrenosum). (4)

The diagnosis may be confirmed by culture (Sabouraud, Mycosel, or blood agar media), although it may be difficult to isolate if overgrown by contaminants. (2,5) PCR and MALDI-TOF mass spectroscopy may identify the organism. (2)
Misdiagnosing protothecosis can delay therapy. In their series of 7 patients, Cullen et al. reported a delay in treatment time that averaged 4 months. (7) There is no standard protocol for treating protothecosis, which may require months of therapy with multiple agents. At-risk patients should be treated aggressively. Surgical excision or debridement is often beneficial for local cutaneous disease. Surgical management is combined with azole antifungals or intravenous amphotericin with a tetracycline for deeper or persistent infections. (5) A novel lipid nanocrystal (LNC) amphotericin B (MAT2203; Matinas Biopharma) is an investigational oral suspension that aims to provide the broad antifungal coverage of conventional amphotericin B with fewer toxicities. It successfully treated a recalcitrant case of protothecosis in a 71-year-old man. (3)
In conclusion, although rare, protothecosis is an underrecognized disorder. Especially in immunocompromised hosts, it should be considered in the differential diagnosis of infectious diseases to avoid misdiagnosis.
Point to Remember: Protothecosis presents as a localized cutaneous infection, olecranon bursitis, or disseminated disease, especially in immunocompromised patients. Although rare, there have been increasing reports of the disease. Dermatologists should consider this diagnosis in patients presumed to have recalcitrant infectious disorders.
Our expert's viewpoint
Vitoria Azulay, MD
Institute of Dermatology Professor Rubem David Azulay
Santa Casa de Misericórdia do Rio de Janeiro
Rio de Janeiro, Brazil
Protothecosis: diagnostic challenge of an emerging disease
Protothecosis is a rare algae infection caused by Prototheca spp that may affect both immunocompetent and immunocompromised individuals, although it is more common in the last group. It affects both sexes equally with a predilection for older individuals. Risk factors include immunosuppression, diabetes, organ transplantation, corticosteroid use, and malignancies.
The most commonly involved species is P. wickerhamii, found in in diverse habitats, such as plants, soil, fresh water, and saltwater. Usually its inoculation is caused by trauma.
Clinically, this disease has a range of clinical presentations which may mimic bacterial infections, fungal infections, and eczema, making the diagnosis challenging. Primarily it presents as cutaneous disease, but it can have a rheumatic involvement (bursitis, fasciitis, and most commonly olecranon bursitis).
Treatment of protothecosis lacks established protocols which may difficult disease management. Disseminated infections require treatment with amphotericin B, whereas localized infections are managed with azole antifungals or surgical excision.
Davies RR, Spencer H, Wakelin PO., Trans R Soc Trop Med Hyg. 1964 Sep;58:448-51. doi: 10.1016/0035-9203(64)90094-x. PMID: 14206703.
Chen Y, Gao A, Ke Y, Zhou X, Lin L, Lu S, Liu Y. Successful Treatment of Cutaneous Protothecosis Due to Prototheca wickerhamii with Terbinafine. Clin Cosmet Investig Dermatol. 2024 Apr 24;17:913-919. doi: 10.2147/CCID.S453620. PMID: 38689756; PMCID: PMC11059624.
Pechacek J, Schmitt MM, Ferrè EMN, Webb T, Goldberg J, Pathan S, Banerjee C, Barber P, DiMaggio T, Quinn A, Matkovits T, Castelo-Soccio L, Nussenblatt V, Lionakis MS. Successful Treatment of Refractory Cutaneous Protothecosis With MAT2203, an Oral Lipid Nanocrystal Formulation of Amphotericin B. Open Forum Infect Dis. 2024 Jul 18;11(8):ofae428. doi: 10.1093/ofid/ofae428. PMID: 39091644; PMCID: PMC11292040.
Rodrigues FT, Santos PFAM, Soares JVDS, Alves MFGS, Azulay-Abulafia L. Two cases of protothecosis in Brazil: When it is not a bacterial, fungal or viral dermatosis. J Dtsch Dermatol Ges. 2023 Sep;21(9):1022-1024. doi: 10.1111/ddg.15143. Epub 2023 Jul 4. PMID: 37402137.
Stephens MR, Aderibigbe O, Steele KT, Elder DE, Glaser L, Jacob J, Rosenbach M. Draining dorsal hand pustules, nodules, and ulcers in a patient with immunosuppression. JAAD Case Rep. 2019 Sep 24;5(10):846-848. doi: 10.1016/j.jdcr.2019.06.016. PMID: 31649969; PMCID: PMC6804474.
Shakoei S, Mohamadi F, Ghiasvand F, Khosravi AR, Kamyab K, Salahshour F. Disseminated protothecosis: Case report and review of the literature. J Cutan Pathol. 2024 Sep;51(9):705-713. doi: 10.1111/cup.14668. Epub 2024 Jun 11. PMID: 38863080.
Cullen GD, Yetmar ZA, Fida M, Abu Saleh OM. Prototheca Infection: A Descriptive Study. Open Forum Infect Dis. 2023 Jun 6;10(6):ofad294. doi: 10.1093/ofid/ofad294. PMID: 37389225; PMCID: PMC10300632.
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April 24, 2025
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