TMPRSS2 and Kallmann syndrome: Based on the absence of the ACE2 and TMPRSS2 genes in the olfactory sensory neurons as well as in the olfactory bulb, contrasting with their presence in supporting cells, stem cells, and perivascular cells, the authors concluded that anosmia and other olfactory disturbances found in patients with COVID-19 is associated with non-neuronal cells (Brann et al., 2020).