NPC1 and obesity due to melanocortin 4 receptor deficiency: Additionally, variation at the NPC1 locus has been associated with several fundamental challenges in medicine including aging, neurodegeneration, obesity, and viral infections, suggesting that variation at the NPC1 loci has widespread relevance beyond the rare NP-C disease (Erickson et al. 2008; Meyre et al. 2009; Tang et al. 2009; Carette et al. 2011).