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Letter
Human Pythiosis
Jakrapun Pupaibool,* Ariya Chindamporn,* Kanitha Patarakul,* Chusana
Suankratay,* Wannasri Sindhuphak,* and Wanla Kulwichit*
*Chulalongkorn University, Bangkok, Thailand
Suggested
citation for this article
To the Editor: Over the past 2 decades, human pythiosis has emerged
as an important parafungal disease; Thailand reports the most cases (1,2).
Given the rarity of this infection in humans and the limited attention
of researchers to the disease, our understanding of its pathogenesis and
other important traits, including its management, await investigation.
We report 2 distinct cases.
The first patient was a 63-year-old woman with hemoglobin AEBart's disease,
a complex thalassemia/hemoglobinopathy syndrome, which required frequent
blood transfusions. Two months before admission, after a major flood and
exposure to standing water for weeks, an abnormal sensation developed
in her right foot, which progressed to pain and intermittent claudication.
Subsequent inability to walk prompted her to seek medical assistance.
At admission, she was febrile with absence of pulses on the right lower
extremity and a diminished pulse on the left. She had a peripheral blood
eosinophilia of 10%. Emergency femoral angiography indicated complete
obstruction of the right common iliac and left internal iliac arteries
(Figure) with collateral supplies via lumbar arteries.
Surgical intervention demonstrated a white clot from aortic bifurcation
down to the right common iliac artery and the superficial and deep femoral
arteries, surrounded by necrotic tissue and enlarged inguinal nodes. Right
femoral embolectomy and aortofemoral bypass were performed. A 10% KOH
preparation of the clot and dissected nodes showed branching septate hyphae.
Cultures of these specimens grew Pythium insidiosum. Itraconazole
solution, terbinafine, and therapeutic vaccines (3)
were administered. Extended-spectrum antimicrobial agents were also given
during her hospital stay to combat nosocomial infections. Progressive
wound necrosis and gangrene of the limbs dictated multiple debridements
and subsequent limb amputations and hip disarticulation. Her clinical
course worsened, and she died 2 months after admission.
The second patient was a 15-year-old boy with β-thalassemia/hemoglobin
E disease, 10 years after splenectomy. The patient received frequent blood
transfusions and monthly intravenous deferoxamine for secondary hemochromatosis.
Six days before admission to our hospital, necrotizing cellulitis of both
legs, unresponsive to intravenous antimicrobial agents, was diagnosed
at a local hospital. The patient reported frequent swimming in standing
water in rice fields. He was febrile with a leukocyte count of 26,000/mm3
and was given broad-spectrum intravenous antimicrobial agents. Severity
of the lesions demanded surgical debridement (Appendix
Figure), which showed necrosis of skin and subcutaneous tissue but
intact fasciae and muscles. Tissue pathology and fungal staining did not
demonstrate the etiologic agent. Surgical tissue Gram's stain and culture
were nonrevealing, but fungal culture grew P. insidiosum after
a few days. Isolates demonstrated white submerged colonies and microscopically
showed sparsely septate hyphae 4–10 μm in diameter. Boiled grass blades
were transferred onto the agar with the growth and incubated at 37°C
for 24 hours. The blades were then put in a container with dilute salt
solution for 2 hours at 35°C. They were subsequently placed on a slide,
and mobile biflagellate zoospores were seen. Serum antibodies to P.
insidiosum by immunodiffusion were detected in both cases. Femoral
angiography showed no abnormalities. Since therapeutic immunogens were
not available during that period, a combination of supersaturated potassium
iodide (SSKI), itraconazole, and terbinafine was initiated. SSKI was discontinued
after a month because of side effects. Lesions were progressive involving
fasciae and muscles and necessitated 2 episodes of surgical debridement
during the first month. The lesions began to improve in the second month
of medical therapy, when skin grafting was performed. The patient remained
well and was discharged after almost 3 months. Medications were continued
for a total period of 6 months. The patient has been well for >2 years.
P. insidiosum in tissues resembles agents of zygomycosis morphologically
but, unlike the latter, rarely stains with hematoxylin and eosin. Various
immunostainings also help identify the organism (4).
With the exception of the facial-cranial form of the disease in the United
States (5), most cases in Thailand occur in patients
with chronic hemolytic anemia; thalassemia-hemoglobinopathy is the most
common underlying disease. Major clinical manifestations include ocular
and craniofacial infections in healthy children, arteritis usually originating
from lower extremities, and chronic subcutaneous abscesses.
Treatment options reported to be successful include supersaturated potassium
iodide for the chronic cutaneous form (2), a combination
of terbinafine and itraconazole in a single case of an acute, severe ocular,
subcutaneous infection (6), and therapeutic vaccination
for severe infections involving major arteries (7,8)
in conjunction with surgery. The first case suggested that, with chronic
pythiosis involving the aorta, effective management is difficult. In the
second case, the laboratory was familiar with P. insidiosum isolation
procedures; therefore, a quick diagnosis was made and early treatment
was instituted. This early form of cutaneous pythiosis is rarely diagnosed
properly by most clinical and pathologic laboratories. Human cases probably
occur worldwide (9) but are underrecognized and
thus, misdiagnosed (5). More research into the
pathogenesis, diagnosis, and new treatment modalities is urgently needed.
Acknowledgments
We thank Leonel
Mendoza for performing immunodiffusion and providing the therapeutic
immunogens and Brian Poligone for a critical review of the manuscript.
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Suggested citation
for this article:
Pupaibool J, Chindamporn
A, Patarakul K, Suankratay C, Sindhuphak W, Kulwichit W. Human pythiosis
[letter]. Emerg Infect Dis [serial on the Internet]. 2006 Mar [date
cited]. Available from http://www.cdc.gov/ncidod/EID/vol12no03/05-1044.htm
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