Background and aim of the work: The recent diffusion with Pandemia of the new Sars-Cov 2 infection [1,2] has introduced into clinical practice the need for the clinician to reconsider innumerable pathologies involving well known vascular risk factors. As a consequence, the treatment and the prophylaxis of the novel severe complications leading to increased mortality and disabling because suddenly urgent. Therefore, it has become necessary to revaluate pathologies incriminated for thrombotic risk even in ‘unsuspected’ young subjects due to the now assessed ability of Coronavirus infection to determine diffuse thrombosis. In fact in the protocols that came into use for the prophylaxis and therapy of Covid-19 infection is now practically validated the use of low molecular weight heparin. In this study the case of a young woman with methylenetetrahydrofolate reductase (MTHFR)  symptomatic deficiency diagnosed in the period of the Covid-19 emergency is reported. The same diagnostic questioning has also been extended to her family affected by this rare disease to prevent complications due to a possible Covid-19 infection.