Various factors and medical conditions, including age, obesity, atherosclerosis, modifiable vascular risk factors, chronic neurological disorders (e.g., Alzheimer's disease, chronic infarction, and autoimmune neuronal disease) as well as acute infectious diseases may affect YKL-40 levels [1]–[4], [23]. The gene discussed is CHI3L1; the disease is obesity due to melanocortin 4 receptor deficiency.