Reduced serum BDNF concentrations were recently described in patients with neurodevelopmental disorders or neurodegenerative diseases (Alzheimer, Parkinson, and Huntington’s), suggesting a possible role for this neurotrophin as an effect biomarker in these diseases (Ciammola et al., 2007; Wang et al., 2015; Amidfar et al., 2020; Gutierrez et al., 2020; Huang et al., 2021; Yi et al., 2021). The gene discussed is BDNF; the disease is neurodegenerative disease.