Notably, the penile tissue of mice with SCD exhibits a reduction in PDE5 expression, which is attributed to the diminished basal bioavailability of NO-cGMP due to decreased eNOS expression and increased oxidative stress (Bivalacqua et al., 2013; Silva et al., 2016b; Musicki et al., 2018; 2020; Pereira et al., 2022). The gene discussed is PDE5A; the disease is Schnyder corneal dystrophy.