Among the above disorders, PCSK1 deficiency is an age-related CDD, with neonatal-onset severe malabsorptive diarrhea, but the intestinal phenotype will disappear later and the patient would even develop obesity with multiple endocrine abnormalities (Jackson et al., 1997; Frank et al., 2013; Pepin et al., 2019). The gene discussed is PCSK1; the disease is obesity due to melanocortin 4 receptor deficiency.