A 78-year-old man developed severe skin lesions that quickly worsened over six months, leading to his death. Despite multiple tests, doctors couldn’t find the cause until he was transferred to Yale, where a rare amoeba was finally identified as the culprit. His case highlights how a common water organism can cause deadly infections in healthy individuals.

The Slow Descent into Darkness

Over half a year, the man’s body was covered in blackened ulcers and necrotic lesions. His face was scabbed, and he had a hole between his mouth and nasal cavity. The wounds started on his legs, showing red nodules that turned dark and ulcerated. As the lesions spread to his arms, neck, and trunk, doctors struggled to find the cause. Initial biopsies showed inflammation but no bacteria or fungi, and his immune system appeared to attack his blood vessels.

He was given immunosuppressant drugs, which only made his condition worse. When he arrived at Yale, he was frail, confused, and had lost significant weight. His lesions kept worsening, and doctors noted he had recently returned from Florida, where he was exposed to algae during cleanup after a hurricane. His medical history included nasal polyps and asthma, for which he used a medication called dupilumab. It was only after a second biopsy and DNA testing that the true cause was revealed: an infection with Acanthamoeba.

The Hidden Threat of Acanthamoeba

Acanthamoeba is a tiny, free-living amoeba found in many water sources, including tap water. While usually harmless, it can cause serious infections in some people. It’s most dangerous for those with weakened immune systems, such as people with HIV, cancer, or on immune-suppressing drugs. Typically, it causes eye infections known as Acanthamoeba keratitis, but it can also infect the brain or other tissues.

In this man’s case, the amoeba likely entered through his nasal passages, as he used sinus rinses with tap water to manage nasal polyps. The amoeba can invade through the nose and spread to other parts of the body. His lesions started on his legs, which is unusual, but the infection can manifest in different ways. The exposure was possibly linked to his time in Florida, where he encountered algae during hurricane cleanup.

Doctors initially suspected immune-related issues, especially since his skin biopsies showed signs of immune attack. But once they identified the amoeba, they started targeted treatment, including a five-drug regimen recommended by health authorities. They also gained approval to try an experimental antibiotic, nitroxoline, which showed some promise. Unfortunately, his condition continued to decline, and he died six weeks after diagnosis, succumbing to multiorgan failure caused by the infection.

Lessons from a Rare but Deadly Infection

This case underscores how a common water organism can turn deadly under certain conditions. It also raises awareness about the risks of using tap water for nasal rinses, especially in vulnerable individuals. The use of immunosuppressive medication like dupilumab may have played a role in his susceptibility, as it suppresses parts of the immune response that might normally fight off such organisms.

While infections with Acanthamoeba are rare, they can be fatal if not caught early. Symptoms can be nonspecific, and diagnosis often takes time. This case highlights the importance of considering rare pathogens in unexplained, rapidly worsening skin infections, especially when standard tests come back negative.

Overall, it reminds us that even seemingly harmless organisms in our environment can cause serious health issues, especially when immune defenses are compromised. Proper water hygiene and cautious use of nasal rinses are vital for preventing such rare but deadly infections.

Inspired by

• https://arstechnica.com/health/2026/05/amoebas-eat-man-alive-over-months-in-puzzling-ultra-rare-cautionary-tale/

Sources

• cdc.gov
• cdc.gov
• nejm.org