ACE2 and COVID-19: Such multi-system involvement characterizing COVID-19 may be attributable to the wide topographic distribution of the viral Angiotensin Converting Enzyme 2 (ACE2) binding receptor, mediating cell invasion, which has been detected in upper and lower respiratory apparatus; gastrointestinal tract, including oral epitheliocytes; exocrine glands, along with salivary ones; cardiovascular and genitourinary systems; skeletal muscles and skin [5,6,7].