A rash that seemed to move across a man's entire body was due to worms crawling under his skin, according to a new report.
The 64-year-old man, who lives in Spain, had been previously diagnosed with metastatic lung cancer and needed to be hospitalized because the cancer had spread to his spine and was pressing on his spinal cord, according to the report, published April 21 in The New England Journal of Medicine. While in the hospital, doctors gave him a high dose of glucocorticoids, a class of steroids that fight inflammation and are sometimes used in cancer patients to help with side effects of chemotherapy and to aid in the treatment of certain cancers.
Four days after receiving the glucocorticoids, the man developed a rash in the form of red, wavy lines all over his body, along with mild diarrhea, according to the authors, from Hospital Universitario 12 de Octubre in Madrid, Spain.
The lesions originated around the anus and had "spread rapidly to the trunk and limbs," according to the report. Doctors outlined some of the lesions with a pen, and 24 hours later, they observed something disturbing: The lesions had migrated from their original locations. In other words, something was crawling under his skin.
The man's stool tested positive for a type of roundworm called Strongyloides stercoralis. This roundworm is found worldwide, but is most common in the tropics, subtropics and in warm temperate regions, according to the Centers for Disease Control and Prevention (CDC).
S. stercoralis larvae dwell in soil, and so people usually become infected through contact with contaminated soil, but they can also become infected through contact with human waste or sewage, according to the CDC. It's unclear how the man became infected, but he worked in sewage management, the report said.
When the larvae come in contact with human skin, they can penetrate the skin and migrate through the body to the small intestine, "where they burrow and lay their eggs," according to the CDC.
The eggs hatch inside the intestine, and most of the larvae are excreted in stool, but some can reinfect a host through a process known as "autoinfection." This happens when the hatched larvae either burrow into the intestinal wall or penetrate the skin around the anus, according to the CDC. The latter appears to have happened in the man's case.
Most people infected with S. stercoralis don't develop symptoms, though some may develop non-specific symptoms such as abdominal pain, nausea, diarrhea or constipation, as well as a rash where the worm entered the skin, according to the CDC. But the infection can be life-threatening in people who take steroid medications, which suppress the immune system.
The man's treatment with glucocorticoids predisposed him to this serious form of the infection, known as "strongyloides hyperinfection syndrome." In this form, the worm's life cycle is accelerated, leading to a much higher number of worms in the body than in a regular case, according to a 2011 paper published in the journal Gastroenterology & Hepatology.
The hyperinfection syndrome can also lead to the spread of the worms to lungs, liver, brain, heart and urinary tract; and can lead to death in up to 80% of cases because the diagnosis often is delayed, according to Medscape.
Fortunately, the man received prompt treatment with the ant-parastic drug ivermectin, and his rash and diarrhea abated, the report said.
Originally published on Live Science.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.