Considering that all patients of Danon disease including female patients with decreased Lamp2 expression due to a heterozygous null mutation and male patients with completely absent Lamp2 expression develop severe cardiomyopathy (Endo et al., 2015; Sugie et al., 2018; Cenacchi et al., 2019), we can deduce that Lamp2 is especially important for the proper function of the heart and that Lamp2 couldn’t function properly and act as a protectant when its protein content decreased to a certain degree. The gene discussed is LAMP2; the disease is cardiomyopathy.