Although the pathogenetic mechanisms are not fully understood, the currently available evidence suggests that the most likely cause of anosmia during COVID-19 infection is an altered function of olfactory sensory neurons left vulnerable and deprived of nutrients, due to the infection and the death of supporting cells, microvillar cells, and vascular pericytes which greatly express angiotensin-converting enzyme 2 (ACE2)5,6. This evidence concerns the gene ACE2 and Kallmann syndrome.