Role of Immunotherapy in Pythium insidiosum Keratitis

Pythium keratitis is a potentially devastating ocular condition. Incidence of Pythium keratitis has been reported in tropical and subtropical areas. In previous reports, there were no effective or standard treatments, and combinations of medication, immunotherapy, and surgery were proposed. Pythium insidiosum antigen immunotherapy (PIAI) showed an acceptable safety profile, but its efficacy is questionable in Pythium keratitis. This retrospective review included 10 eyes from 10 patients. All cases were confirmed diagnosis of P. insidiosum keratitis by culture and/or polymerase chain reaction. Three doses of PIAI were injected at 2-week intervals in all patients. The infiltration diameter ranged from 5.2 mm to total corneal involvement, and eight cases (80%) had hypopyon. Therapeutic penetrating keratoplasty (TPK) or scleral graft were undertaken in nine cases. Enucleation was done in one case on the first visit. A second TPK was undertaken in three cases, and two globes were saved. Two cases in the globe salvage group received voriconazole via eyedrops and intracameral injection. No case received either linezolid or azithromycin. Three of nine eye globes (33.33%) were saved. PIAI did not show efficacy in the treatment of Pythium keratitis. Radical surgery including resurgery in recurrence is an approved effective treatment. The recently reported medications may offer supportive management.