Researchers from the U.S. Centers for Disease Control and Prevention (CDC) identified a unique medical case in which a 41-year-old HIV patient died because of a tapeworm infection that led to the growth of cancer-like cells in different parts of his body.
The patient from Colombia came to the attention of the CDC in 2013. His immune system was already compromised because of the HIV infection. He had trouble breathing, lost weight and had a fever. Malignant tumors also grew on his lungs, adrenal glands and liver, but doctors in Columbia noticed that the tumors looked unusual. Lymph nodes also became so enlarged in the patient's neck that he couldn't move his head.
Samples were sent to the CDC for further analysis. Experts then discovered after numerous tests that the cancerous cells, which looked like clumps and sheets, were not human cells but were the eggs of the dwarf tapeworm Hymenolepis nana.
"We knew invertebrates can grow tumors, but the fact that one can invade and disseminate in a human and make them sick just really, really defied belief," said Dr. Atis Muehlenbachs, lead author of the CDC study published in the New England Journal of Medicine.
Biologist Peter Olson from the Natural History Museum who was involved in the study said that tapeworms are most common in areas with poor sanitation, and that these parasites live in the guts of more than 75 million people but don't usually cause severe problems.
The dwarf tapeworm is the only known parasite of its species that is able to reproduce entirely in the human gut and create new generations in the host's stool, Olson said. This was why the parasites had reproduced inside the patient's body without needing to be re-exposed to external surroundings.
Some of the tapeworm's larva cells went awry and proliferated as cancer, Olson explained.
The researchers from the CDC compared the tapeworm cells found in the HIV patient to normal tapeworm genes. They found structural abnormalities and broken genes, which were likely the same genes that get broken in human cells and cause malignant cancer.
Meanwhile, doctors never had the chance to provide the patient with a specific treatment because his condition was very rare. When doctors knew what was happening, the patient slipped into a coma and died 72 hours after the molecular diagnosis.
Experts are still unsure what kind of treatment would help future cases similar to this one.