Researchers have linked gene expression with the disease process that lies behind chronic fatigue syndrome (CFS).
The new study has found that blood may hold key information about what goes on in the brain of CFS patients.
CFS is marked by severe, chronic mental and physical exhaustion, arising in a previously healthy and active person.
The study was conducted by a team of researchers led by Professor Andrew Lloyd at the University of New South Wales.
As part of the research, scientists examined six million pieces of gene expression information to study the differences in gene expression patterns in the blood of 15 individuals who either recovered promptly after acute glandular fever or developed prolonged illness called post-infective syndrome.
Gene expression is significant because it is the process by which a gene's DNA sequence is converted into the proteins that ultimately determine the manifestations of disease.
Researchers studied the expression of 30,000 genes in the blood, testing each person between four and five times over a 12-month period.
The study found that there were just 35 genes whose pattern of expression correlated closely with the key symptoms of the illness when examined from onset through to recovery.
"These genes might point to the nature of the disease process that underlies CFS, which is currently unknown," Professor Lloyd said.
The findings of the study were published in the Journal of Infectious Diseases.