Can atypical dysgeusia in depression be related to a deafferentation syndrome?

Atypical dysgeusia such as having the sensation of a sweet tooth is an uncommon clinical presentation in severe depression. First, we present the case of a 67 year-old-man admitted to the psychiatric ward for depression after a suicide attempt by drug ingestion. The patient manifested a sweet taste sensation in the upper and lower gums that increased with mood swings and notably with severe depressive symptoms. Blood tests showed an elevated serum creatinine level (115 μmol/L), a normocytic anemia (hemoglobin 6.5 mmol/L; MCV 96 fL) and a deficit in vitamin B12 (122.4 pmol/L). The patient received vitamin B12 supplementation and was treated with clomipramine, lithium, mirtazapine, modafinil, and olanzapine. He was discharged after improvement of his depressive symptoms and decrease in the sweet taste. On follow-up, the patient's dysgeusia had subsided. Second, we hypothesize that the atypical dysgeusia may have been induced by vitamin B12 deficiency and medical comorbidities, leading to deafferentation (development of erroneous mouth mucosae sensations felt by the patient). This could have been increased by depression. Dysgeusia in elederly patients with depression should be extensively investigated in order to elucidate somatic contributing factors but it may not resolve until improvement of the depressive symptoms.