Decreased Parotid Saliva Gustin/Carbonic Anhydrase VI Secretion: An Enzyme Disorder Manifested by Gustatory and Olfactory Dysfunction

Abstract

Background: Taste and smell dysfunction has been reported to occur in patients with a variety of clinical problems. We wanted to investigate a specific group of patients in whom taste and smell dysfunction occurred putatively related to a specific biochemical abnormality in a salivary growth factor [gustinlcarbonic anhydrase (CA) VI] considered responsible for maintenance of taste bud function. Methods: Eighteen patients developed loss and/or distortion of taste and smell after an acute influenza-type illness. They were evaluated clinically, by psychophysical tests of taste and smell function, by measurement of parotid salivary gustin/CAVI by a radioimmunoassay and by measurement of serum, urine, and salivary zinc. Biopsies of circumvallate papillae were obtained in 6 patients and examined by transmission electron microscopy. Similar studies were performed in 55 asymptomatic volunteers with biopsies of circumvallate papillae performed in 4. Results: Taste and smell acuity were impaired in patients compared with healthy volunteers and parotid gustin/CAVI, salivary, and serum zinc concentrations were lower in patients than in healthy volunteers. Taste buds in circumvallate papillae of patients exhibited severe vacuolization, cellular degeneration, and absence of dense extracellular material. Conclusions: These results describe a clinical disorder formulated as a syndrome of hyposmia (decreased smell acuity), hypogeusia (decreased taste acuity), dysosmia (distorted smell function), dysgeusia (distorted taste function), and decreased secretion of parotid saliva gustin/CAVI with associated pathological changes in taste bud anatomy. Because gustin/CAVI is found in humans only in parotid saliva and has been associated with taste bud growth and development these results suggest that inhibition of synthesis of gustin/CAVI is associated with development of taste bud abnormalities and thereby loss of taste function.