One study investigating genetic variability due to poly-amino acid repeats using supervised Machine Learning (Baldassarri et al., 2021) compared the genotypes of patients with extreme clinical manifestations (asymptomatic vs. severe), and found an association between the poly-glutamine (Q) repeat number of the AR gene, serum testosterone concentrations, and COVID-19 outcome in male patients. The gene discussed is AR; the disease is COVID-19.