Man Dies From Rare Flesh-Eating Amoeba Infection

A case report published in the April 2026 issue of the journal Emerging Infectious Diseases describes a rare and fatal disseminated infection caused by Acanthamoeba, a free-living amoeba. The patient, a 78-year-old man, developed progressive necrotic skin lesions that eventually spread across his entire body, leading to his death.

The findings, detailed by researchers from the Yale School of Medicine and Brigham and Women’s Hospital, highlight the risks associated with opportunistic infections in patients using specific advanced therapies for chronic inflammatory conditions.

Clinical Progression and Misdiagnosis

The patient sought care at a tertiary-care academic hospital after a six-month history of worsening skin lesions. These lesions first appeared on his legs as reddish nodules that eventually developed central darkening. Over time, some of these nodules evolved into deep ulcers, while others progressed to necrosis with eschar.

The infection eventually spread to involve the head, neck, trunk, and all extremities, though the patient’s back remained spared. In addition to the skin deterioration, the man reported a weight loss of 16 pounds, although he did not experience a fever.

Initial diagnostic efforts complicated the case. Skin biopsies revealed focal granulomatous medium-vessel vasculitis with neutrophilic infiltrates. Because early stains for fungi and acid-fast bacilli were negative, clinicians initially suspected the vasculitis was immune-mediated rather than infectious.

Based on this suspected immune-mediated cause, the patient was treated with aggressive immunosuppressive therapies. These included rituximab, cyclophosphamide, mycophenolate mofetil, and prednisone at doses reaching 80 mg daily. Rather than improving, the patient’s condition worsened under this regimen.

Environmental Exposure and Risk Factors

The patient’s medical history included asthma and sinus polyposis, for which he had been treated with dupilumab for 18 months. Dupilumab is a monoclonal antibody that inhibits interleukin-4 and interleukin-13 cytokines to suppress the T2 inflammatory response.

Investigators identified a likely source of exposure during the patient’s time in Florida. While assisting with cleaning efforts following a hurricane, the man had been exposed to knee-deep brackish water and red tide. He also performed regular nasal rinses using normal saline.

Understanding Acanthamoeba

Acanthamoeba species are free-living amoebae found commonly in soil and water. While they are most frequently associated with keratitis—an infection of the cornea often linked to contact lens use—they can cause invasive disease in immunocompromised individuals.

Nonkeratitis invasive disease is typically opportunistic and often fatal. The researchers noted that the population at risk for such infections is growing as more drugs are developed that target specific parts of the inflammatory cascade, potentially creating windows of vulnerability for rare pathogens.

Once the disseminated Acanthamoeba infection was correctly diagnosed, the patient was started on multidrug therapy that included nitroxoline. Despite this intervention, the infection had progressed too far to be reversed.

The report serves as a clinical warning that Acanthamoeba can present as infectious vasculitis, which may mimic autoimmune conditions and lead to the dangerous administration of immunosuppressants in a patient already fighting an active infection.