74. Pythium insidiosum necrotizing fasciitis in an immunocompetent patient exposed to a New Mexico hot spring: a rare human case of “swamp cancer” in the southwest United States
Session: Posters in the Park: Posters in the Park
Wednesday, October 3, 2018: 5:30 PM
Room: N Hall D Opening Reception and Posters in the Park Area
  • Pythium ID Week Poster.pdf (1021.5 kB)
  • Please avoid the use of abbreviations.

    Final Diagnosis:

    Pythiosis (Pythium insidiosum infection)

    Brief history of the Present Illness:

    A 58-year-old male without known immunocompromising conditions presented with slowly expanding bilateral lower extremity erythematous, indurated and painful skin lesions with central ulceration and necrosis. The lesions had progressed over approximately four weeks prior to presentation. He had sustained minor superficial skin abrasions while swimming in a New Mexico hot spring six days before first noticing the skin lesions. He was initially treated with antibiotics for presumed cellulitis. Due to clinical progression with enlargement and central ulceration and necrosis of the right leg lesion he was emergently referred to dermatology. He had no other symptoms associated with the progressive skin lesions, denying fevers, chills, night sweats, weight loss and swollen lymph nodes.

    Past Medical History including allergies (if relevant):

    Mild intermittent asthma
    Cervical disk disease

    Key Medications (if relevant):

    Budesonide/Formoterol 160/4.5mcg 2 puffs BID

    Doxycycline 100mg by mouth twice daily

    Amoxicillin/clavulanate 875/125mg by mouth twice daily

    Epidemiological history (if relevant, such as habits, social and family history, animal exposures or travel):

    Tobacco: occasional cigar smoker, smoked cigarettes x10 years, quit in 1990

    Alcohol: 2-3 drinks per day (beer and/or scotch)

    Denies recreational drug use

    Sexual: in monogamous relationship with female partner and denies STI history

    Works administrative job for VA

    Last international travel to Japan in 8/2017

    Pets: Iguana, multiple snakes, 5 birds, dog

    Has outdoor fish pond at home – denies contact with pond water

    Denies unusual dietary habits (raw meat/unpasteurized dairy)

    Water exposure: 5-6 days before skin lesions appeared he spent two days at a New Mexico hot spring and waded in multiple pools

    Physical Examination: General description, vital signs, and other relevant physical findings. For example, “The patient appeared well. The blood pressure was 120/80 mm Hg, pulse 72 beats per minute, temperature 98.6oF (37.0oC), and respirations 20 breaths per minute. The examination was otherwise normal.” Please refer to appropriate figures of physical findings if provided (Figure 1, Figure 2, etc.). Please avoid the use of abbreviations.

    The patient was a well-appearing adult male in no acute distress. The blood pressure was 131/87 mm HG, pulse 77 beats per minute, temperature 97°F (36.1°C), and respirations 20 breaths per minute. The examination was significant for the presence of two well circumscribed indurated, erythematous plaques approximately 2x2 cm and 10x6 cm in diameter on the right lower extremity, the larger plaque medial and proximal to the ankle and the smaller plaque anterior and distal to the knee. The inferior lesion had central ulceration and necrosis [Figure 1]. An approximately 3x3 cm extremely indurated, mildly erythematous, mildly scaly plaque was present on the medial left lower extremity proximal to the ankle [Figure 2].

    Studies: Relevant laboratory findings (with units of measurement and normal reference ranges as these vary among institutions), radiology, etc. For example, “The hematocrit was 35.0% (reference range 41.0-53.0 in men), and the other routine laboratory test results were normal. A chest radiograph revealed a pulmonary nodule (1 cm in diameter) in the right upper lung field).” Please include pertinent positives and negatives. Refer to figures if appropriate.

    The white blood cell count was 10.8x103 cells/ µl (reference range 3.8-10.6 x103 cells/ µl) with white blood cell count differential with mild eosinophilia at 7.2% (reference range 0-7%) and absolute eosinophil count of 780 x103 cells/ µl. The platelet count was elevated at 463 x103 cells/ µl (reference range 150-440 x103 cells/ µl). Other complete blood count parameters including hemoglobin and hematocrit were within normal range. The serum creatinine was 1.0mg/dL (reference range 0.7-1.2 mg/dL). The alkaline phosphatase was elevated at 102 U/L (reference range 32-91 U/L) and gamma-glutamyl transferase was elevated at 201 IU/L (reference range 7-50 IU/L). Total bilirubin, aspartate aminotransferase, alanine aminotransferase levels were within normal range. The erythrocyte sedimentation rate was elevated at 27 mm/hour (reference range 0-20 mm/hr). Other routine laboratory test results were normal. A venous Doppler ultrasound of the right lower extremity revealed no evidence of deep vein thrombosis but did reveal severe subcutaneous edema of the distal right leg worse along the medial aspect of the ankle.

    Clinical Course Prior to Diagnosis (if relevant): Note Figures if appropriate.

    Skin biopsies were obtained and the patient was admitted for diagnostic and therapeutic management. Skin biopsies revealed ribbon-like hyphae with rare septae on Grocott’s methenamine silver stain [Figue 3]. Treatment with amphotericin B and posaconazole was initiated. Multiple surgical debridements were performed. Necrotic fascia and muscle deep to the distal right lower extremity skin lesion was identified and debrided. Necrotic fascia was identified and debrided deep to the left lower extremity lesion. Additional tissue samples were sent for histopathology and culture. Tissue samples were plated directly onto Sabouraud-dextrose agar and were also sent to a reference lab for fungal culture. Three days after tissue samples were plated onto Sabauroud-dextrose agar, fine, white hyphae were noted to be growing on agar multiple plates [Figures 4, 5]. A subculture of this material was also sent out to a reference lab for fungal culture and identification. The patient appeared to respond well to aggressive surgical debridement and treatment with amphotericin B and posaconazole. Prior to identification of the organism growing in culture he was discharged on continued oral posaconazole. After discharge the same organism was identified from both a tissue sample sent directly for fungal culture and from the subculture that had been sent out to a reference lab. At his outpatient follow-up visit a week after he was discharged, progression of erythema and induration surrounding the previously debrided lesions was noted which raised concern for progression of infection [Figure 6]. He was admitted and underwent additional exploration of his wounds and debridement. Extensive tissue necrosis was noted surrounding the previously-debrided right lower extremity wound leading to a below-the-knee amputation. Tissue samples sent for histopathology were again notable for abundant ribbon-like hyphae with rare septae on Grocott’s methenamine silver stain [Figure 7].

    Differential Diagnosis:

    1. Mucormycosis
    2. Basidiobolomycosis
    3. Conidiobolomycosis
    4. Pythiosis
    5. Aspergillosis

    Diagnostic Procedure(s) and Result(s):

    Pythium insidiosum was identified via 18S ribosomal RNA gene sequencing from both a tissue sample and subculture sent to reference laboratories.


    An immunotherapeutic veterinary Pythium antigen vaccine was administered along with transition to itraconazole, terbinafine, minocycline, and caspofungin. At two month since right below-the-knee amputation, the patient’s left leg has been salvaged and he has no ongoing evidence of pythiosis.

    Brief Discussion of Differential/Major Teaching points of case:

    Pythium insidiosum, a fungus-like parasitic oomycete found in standing water, mainly infects non-human mammals1. Human pythiosis has been associated with hemoglobinopathies and has only rarely been reported in North America2, 3. Four clinical syndromes have been described: cutaneous/subcutaneous, vascular, ocular and disseminated2.

    This case highlights several important features of human pythiosis. It is frequently mistaken for mucormycosis due to similar histopathologic appearance3. Little is known about managing this disease due to its rarity in human hosts. Treatments are largely based upon limited case reports and series. Pythium insidiosum is resistant to traditional antifungals as it lacks ergosterol in its plasma membrane1. However, combination therapies may provide synergistic activity against this organism4, 5. An experimental immunotherapeutic Pythium insidiosum vaccine developed for equine and canine pythiosis can be utilized in human cases2. Most importantly, early and aggressive surgical debridement with confirmed negative margins is necessary for effective treatment2.

    Final Diagnosis:



    1. Gaastra W, Lipman LJ, De Cock AW, et al. Pythium insidiosum: an overview. Vet Microbiol. 2010 Nov 20;146(1-2):1-16. PMID 20800978
    2. Krajaejun T, Sathapatayavongs B, Pracharktam R, et al. Clinical and epidemiological analyses of human pythiosis in Thailand. Clin Infect Dis. 2006 Sep 1;43(5):569-76. PMID 16886148
    3. Salipante SJ, Hoogestraat DR, SenGupta DJ, et al. Molecular diagnosis of subcutaneous Pythium insidiosum infection by use of PCR screening and DNA sequencing. J Clin Microbiol. 2012 Apr;50(4):1480-3. PMID 22205808
    4. Jesus FP, Loreto ÉS, Ferreiro L, et al. In Vitro and In Vivo Antimicrobial Activities of Minocycline in Combination with Azithromycin, Clarithromycin, or Tigecycline against Pythium insidiosum. Antimicrob Agents Chemother. 2015 Oct 12;60(1):87-91. PMID 26459895
    5. Jesus FP, Ferreiro L, Loreto ÉS, et al. In vitro synergism observed with azithromycin, clarithromycin, minocycline, or tigecycline in association with antifungal agents against Pythium insidiosum. Antimicrob Agents Chemother. 2014 Sep;58(9):5621-5. PMID 25001300


    • Please identify as Figure 1, Figure 2 etc, and place the image(s) in the PowerPoint presentation being submitted. Please remove patient identifiers (name, medical records number, date, etc.) from each image to protect patient confidentiality.

    • Below, please note the type of image (CT scan, MRI, radiograph, physical finding photo, laboratory slide which identifies the specific stain used, etc.) and the legend/findings to accompany the individual figures.

    Figure #, location of image, type of image, legend

    1. Distal right lower extremity skin lesion (this photo is most representative of the case)
    2. Distal left lower extremity skin lesion
    3. Laboratory slide, skin biopsy, Grocott’s methenamine silver stain
    4. Growth of white hyphae on Sabauroud-dextrose agar plate
    5. Growth of white hyphae on Sabauroud-dextrose agar plate
    6. Right lower extremity wound with wound-vacuum system in place
    7. Laboratory slide, skin biopsy, Grocott’s methenamine silver stain

    Luke Meininger, MD1, Rupal Mody, MD2, Jeff Sherwood, MD2 and Matthew Perkins, MD3, (1)Internal Medicine, William Beaumont Army Medical Center, El Paso, TX, (2)Infectious Disease, William Beaumont Army Medical Center, El Paso, TX, (3)Infectious Diseases, William Beaumont Army Medical Center, El Paso, TX


    L. Meininger, None

    R. Mody, None

    J. Sherwood, None

    M. Perkins, None

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