Patients suffering from systemic lupus erythematosus (SLE) have been found to have a decreased sense of smell, a new study has revealed.
SLE is an autoimmune disease that sometimes involves the central nervous system in a condition known as neuropsychiatric SLE (NPSLE).
The sense of smell is a complex process of the central nervous system that involves specific areas of the brain.
Research in mice has shown that NPSLE-like symptoms and olfactory impairment might be induced by autoimmune mechanisms that target specific areas of the brain, but this has not been explored.
The new study, led by Yehuda Shoenfeld of Chaim Sheba Medical Center in Tel-Hashomer, Israel, involved 50 SLE patients and 50 age and sex-matched controls.
Researchers evaluated three levels of olfactory function: threshold (identifying a stick with an odour from among sticks that didn't have an odour); discrimination (differentiating between two smells); and identification of a smell from among four options. The three scores were combined to form a total TDI score.
The results showed that significant olfactory deficits in the SLE patients compared with the controls. SLE patients showed a decrease in olfactory function in both the threshold and discrimination tests.
Also, the study found that patients with more active disease and past NPSLE manifestations had significantly lower TDI scores.
Previous study in mice has shown that injection of antibodies linked to NPSLE manifestations induced olfactory deficit and that these antibodies can bind and penetrate cells in limbic areas of the brain, which are associated with the sense of smell.
Also, magnetic resonance imaging has recently shown limbic system involvement in SLE patients.
"Although the exact mechanism of olfactory impairment has yet to be elucidated, the possibility of an immune-mediated mechanism is intriguing," the authors said.
The study was published in the May issue of Arthritis and Rheumatism.