Pythium insidiosum is a fungus that causes disease in both animals and humans. Human
pythiosis is an emerging disease in the tropical, subtropical, and temperate regions of the world, occurring in localized and systemic or vascular forms. Most patients with arterial
pythiosis have an underlying
hemoglobinopathy, such as
thalassemia. A case is presented of a thalassemic horse stable worker who developed an ulcerative cutaneous lesion on the lower left leg followed by progressive ascending involvement of the arteries of that extremity with a
necrotizing arteritis with
aneurysm formation. P. insidiosum was not isolated from the
ulcer by culture or wet
potassium hydroxide preparations but was diagnosed by histopathologic study of a biopsy. P. insidiosum
infection was quickly confirmed by immunoblot method, aiding in preoperative decision making. Many systemic
antibiotics or antimycotics have not been effective in the treatment of systemic
pythiosis, and radical surgical removal of all infected tissue is the only method to ensure patient survival. An orally administered saturated
solution of
potassium iodide,
amphotericin B-oral
solution, and
terbinafine has succeeded only in the cutaneous form but had no favorable effect on vascular
pythiosis. It is likely that
immunotherapy, successfully used in animal
pythiosis, may be beneficial in the treatment of human vascular
pythiosis.