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Decrease in sense of smell seen in lupus patients

The sense of smell is a complex process of the central nervous
system that involves specific areas of the brain. In fact, olfactory
dysfunction is seen in various central nervous system disorders that
involve immune-mediated mechanisms, such as Parkinson's disease,
schizophrenia, Alzheimer's disease and multiple sclerosis. Systemic
lupus erythematosus (SLE) is an autoimmune disease that sometimes
involves the central nervous system in a condition known as
neuropsychiatric SLE (NPSLE).

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. A new study assessed olfactory
function in SLE patients and found that there is a decrease in the
sense of smell compared with healthy controls. The study was published in the May issue of Arthritis & Rheumatism.

Led by Yehuda Shoenfeld of Chaim Sheba Medical Center in
Tel-Hashomer, Israel, the study involved 50 SLE patients and 50 age and
sex-matched controls. Researchers evaluated three levels of olfactory
function: threshold (identifying a stick with an odor from among sticks
that didn't have an odor); 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 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. In
addition, the study found that patients with more active disease and
past NPSLE manifestations had significantly lower TDI scores. Past
research 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. In addition, 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 note.

The incidence of olfactory dysfunction in the general population is
a matter of debate. About one percent of the population is believed to
have a loss of the sense of smell; in the study, loss of smell was seen
only in SLE patients, 10 percent of whom suffered from this condition.
The importance of the sense of smell is easy to appreciate, since the
inability to detect odors in daily life, for example in food that has
spoiled or leaks in a gas line, could seriously compromise a person's
health.

The authors point out that olfaction is unfamiliar territory for
rheumatologists and immunologists, but results from this and other
studies demonstrate that an autoimmune mechanism may play a role in
olfactory impairment. They conclude that "smell decrement has been
found to be an early and predictive sign in several CNS diseases, and
therefore, might be a useful and easy tool for the physician in early
diagnosis of CNS involvement in autoimmune diseases."

LINK: http://www.physorg.com/news160322968.html