The studies also found a double whammy in these patients nasal mucus. Normal mucus contains not only growth factors to allow new olfactory receptor cells to function, it also contains death factors that kill the aging receptor cells (a normal process of programmed cell death, or apoptosis), making way for the new. The congenital smell loss patients had five to 10 times the concentration of these death factors as do people who can smell. That guaranteed that the high concentration of death factor would destroy any receptor cell growth that was able to take place.
After determining the family of enzymes to which the growth and death factors belong and defining the biochemical pathway responsible for these factors, Dr. Henkin was able to treat these patients with PDE inhibitors that increase the concentration of growth factors and inhibit the secretion o death factors in nasal mucus. The treatment has been successful in restoring smell function in some of these patients, with the higher the dose and longer the use having the greatest effect.