Treatment of Pythiosis

Dear Editor: Due to its rising global incidence, I have dedicated years to studying pythiosis, a rare yet deadly infectious disease caused by Pythium insidiosum.1 Pythiosis typically presents with the infection of the artery, eye, gastrointestinal tract, and skin, and if left untreated, it can lead to organ loss or even death. In recent decades, a deeper understanding of P. insidiosum has been seen across molecular, serological, and histological studies, enhancing clinical awareness and diagnostic advancements.1, 2 Traditionally mistaken for a fungus because of its microscopic appearance, P. insidiosum was treated with antifungal medications like terbinafine and amphotericin B.3, 4 Molecular research clarifies that P. insidiosum is an oomycete, more closely related to algae, with significant biological differences from fungi, impacting drug efficacy.5 Since the 1980s, P. insidiosum antigen immunotherapy (PIAI) has emerged as a treatment alternative, with ongoing enhancements to increase efficacy.6 Surgery often serves as a last resort to limit the disease progression or to save lives.7 Current treatment strategies for pythiosis include antimicrobial drugs, PIAI, and surgery. Antimicrobial susceptibility testing reveals a higher sensitivity of P. insidiosum to antibacterials like macrolides, oxazolidinones, and tetracyclines, reducing the reliance on surgery.8 Though less effective, antifungals, sometimes in combination with antibacterials, can treat pythiosis.9, 10 PIAI, prepared by crude antigen extract of P. insidiosum, is beneficial for humans and animals with pythiosis, potentially reducing surgery needs and increasing survival rates. However, its efficacy varies across different disease manifestations.6 Surgical intervention, typically reserved for unresponsive cases, ranges from organ-preserving procedures to more radical approaches like amputation, depending on disease progression.2, 3, 7 Additional treatments, including dimethyl sulfoxide, potassium iodide, steroids, ethanol, and mefenoxam, applied singly or combined, have shown promise in treating specific pythiosis forms.11, 12 Treatment is the most challenging aspect of pythiosis, but there is hope. The morbidity and mortality of affected patients remain high. However, with continued attention and basic/clinical research by the medical community, we can gain insight into the disease and find a better way of pythiosis control, potentially improving their clinical outcomes.