(RxWiki News) Researchers have found amyotrophic lateral sclerosis (ALS) may be caused by a retrovirus, a virus composed not of DNA but of RNA (ribonucleic acid).
Most cases of ALS, or Lou Gherig's disease, do not appear to have a genetic cause and often arise sporadically. Researchers had previously identified a protein known as reverse transcriptase, a product of retroviruses such as HIV, in ALS patients' blood serum samples, which suggested a retrovirus may be implicated in the disease. (HIV is a retrovirus.)
For the study, Avindra Nath, M.D., a professor of neurology at the Johns Hopkins University School of Medicine, and colleagues looked at brain samples from 62 people, 28 of whom had died from ALS, 12 who expired from chronic diseases such as cancer, 10 who had died from accidents and 12 who died from Parkinson's disease, which is another neurodegenerative disease.
Researchers looked for messenger RNA (mRNA) transcripts from retroviruses, a chemical signature that retroviruses were active in these patients. They found mRNA transcripts that came from human endogenous retrovirus K (HERV-K), one of the thousands of retroviruses that became a part of the human genome after infecting our ancestors long ago.
The study suggests HERV-K may be the ALS retrovirus researchers have sought to uncover.
Dr. Nath said that researchers had never before found a retrovirus for ALS, "so this opens up a whole new area."
The finding may lead to better treatment for ALS using antiretroviral drugs specific to HERV-K.
ALS afflicts about 5,600 Americans each year. Considered a motor neuron disease, the condition usually kills patients within six years of diagnosis. Symptoms include muscle weakness that does not go away and muscle atrophy, among many others.