STXBP3 and obesity due to melanocortin 4 receptor deficiency: Munc18‐3 is ubiquitously expressed, but reduced levels of Munc18‐3 are linked to obesity (Garrido‐Sanchez et al, 2013) and glucose intolerance (Oh et al, 2005; Bergman et al, 2008), mutations in VPS45 lead to severe congenital neutropenia (Vilboux et al, 2013), and mutations in VPS33B cause arthrogryposis–renal dysfunction–cholestasis (ARC) syndrome (Gissen et al, 2004).