Swamp cancer: a case of human pythiosis and review of the literature

Abstract

Pythiosis is an infection caused by the aquatic oomycete Pythium insidiosum. Commonly known as 'swamp cancer' in veterinary pathology, pythiosis is now considered an emerging human disease associated with significant morbidity and mortality. However, because clinical information is limited, many healthcare providers, including dermatologists, are unfamiliar with this diagnosis. To increase awareness of this life-threatening infection, a case of cutaneous pythiosis is presented. We describe a middle-aged man with acute myeloid leukaemia who presented with necrotizing haemorrhagic plaques on his thighs after a weekend of freshwater boating. Histological examination of a biopsy specimen showed invasive fungal hyphae associated with dense perivascular inflammation and vessel damage. Diagnostic testing on tissue culture revealed growth of P. insidiosum. Despite multiple debridements and antifungal therapy, the patient died within 2 weeks of presentation. There are four clinical presentations reported in human pythiosis. Pythium insidiosum infection should be considered in any patient with a suggestive exposure history and fungal elements found on histological examination or in culture. Identification of the organism can be difficult, so polymerase chain reaction and serological assays can be useful in making a diagnosis. To improve clinical outcomes, early combination therapy with antifungals and surgery is needed.

Evaluation of antifungal effect and toxicity of xanthyletin and two bacterial metabolites against Thai isolates of Pythium insidiosum

“…It is well known that the therapy of pythiosis has posed a challenge in recent decades as the current treatment options are highly variable and often lead to failure 14 . Therefore, many studies have searched for antimicrobial agents, natural compounds or secondary metabolites from microorganisms against P. insidiosum and results of in vitro testing are quite promising 6,7,[15][16][17][18][19][20][21] .…”

The Human Gut Colonizer Blastocystis Respires Using Complex II and Alternative Oxidase to Buffer Transient Oxygen Fluctuations in the Gut

“…It includes major plant pathogens, such as Phytophthora , but also diatoms which are major primary producers in the world's oceans. Together with Pythium (Hilton et al, 2016 ), Blastocystis is thought to be the only human pathogen in this eukaryotic lineage. However, reports about its supposed pathogenicity or role in disease are conflicting (see for example Miller and Minshew, 1988 ; Clark et al, 2013 ; Stensvold and van der Giezen, 2018 ).…”

Recent update in diagnosis and treatment of human pythiosis

“…If left untreated, cutaneous/subcutaneous infection could progress to vascular pythiosis, which can lead to amputation of the affected limb (Krajaejun et al, 2006b;Khunkhet, Rattanakaemakorn & Rajatanavin, 2015). Craniofacial infection, such as periorbital/orbital necrotizing cellulitis, is a rapid-onset clinical feature observed in children and young adults with a recent history of exposure to wetland (Krajaejun et al, 2006b;Hilton et al, 2016;Kirzhner et al, 2015;Triscott, Weedon & Cabana, 1993). Rarely, P. insidiosum infection can disseminate to a visceral organ and result in mortality (Krajaejun et al, 2006b), which in a patient with gastrointestinal involvement leads to upper gastrointestinal bleeding, bloody mucous stools, gastric/ileal ulcer, and peritonitis (Krajaejun et al, 2006b).…”

“…When stimulate with P. insidiosum zoospore, peripheral blood mononuclear cells collected from thalassemic patients showed lower level of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interferon gamma (IFN-γ) production, compared with the non-thalassemic controls (Ud-Naen et al, 2019). Other hematologic disorders that predispose individuals to vascular pythiosis include paroxysmal nocturnal hemoglobinuria, aplastic anemia, myelodysplasia, idiopathic thrombocytopenic purpura, and leukemia (Krajaejun et al, 2006b), and to a lesser extent, young age, alcoholism, malnourishment, immunosuppression, HIV infection, cancer, and neutropenia (Krajaejun et al, 2006b;Pan et al, 2014;Shenep et al, 1998;Chitasombat et al, 2018a;Hoffman, Cornish & Simonsen, 2011;Hilton et al, 2016;Kirzhner et al, 2015;Franco et al, 2010;Chitasombat et al, 2018b).…”

“…There are only a few cases of carotid artery involvement, an extremely rare but potentially fatal condition that results in meningitis, cerebral septic emboli, brain abscesses, and death. Patients with an immunosuppressed or neutropenic condition may present with abrupt-onset infection (i.e., within days after the onset of symptoms), with or without a history of exposure to aquatic habitats (Chitasombat et al, 2018a;Hoffman, Cornish & Simonsen, 2011;Hilton et al, 2016), and develop necrotic skin lesions/cellulitis that progress to vascular infections shortly afterward (within a few days or weeks). Early recognition of pythiosis and the use of a rapid laboratory test leads to prompt and definitive therapy.…”