RAB3 and RAB27 have been previously implicated in the exocytosis of pituitary hormones (75–77) and insulin (78–80), and it has been suggested that reduced activation of RAB3 and RAB27 may lead to problems in hormone secretion in patients with biallelic MADD variants (37). The gene discussed is INS; the disease is multiple acyl-CoA dehydrogenase deficiency.