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

• Published in: British journal of dermatology (1951) Vol. 175; no. 2; pp. 394 - 397
• Main Authors: Hilton, R.E., Tepedino, K., Glenn, C.J., Merkel, K.L.
• Format: Journal Article
• Language: English
• Published: England 01.08.2016
• Subjects: Adult; Dermatomycoses - diagnosis; Diagnosis, Differential; Fatal Outcome; Fever of Unknown Origin - parasitology; Humans; Male; Oomycetes; Pythiosis - diagnosis; Pythium insidiosum; Skin Diseases, Parasitic - diagnosis; Thigh
• ISSN: 0007-0963; 1365-2133
• DOI: 10.1111/bjd.14520

Summary 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. What's already known about this topic? Pythiosis is an endemic infectious disease in Thailand associated with high morbidity and mortality; however, it is rare in North America. Very few cases of cutaneous disease have been reported in the literature. What does this study add? We present a case of pythiosis in North America, and review the previously reported cases of cutaneous pythiosis. Our case highlights the importance of increased awareness of this infectious disease in order to facilitate early recognition and treatment.