Each BSCL type is identified by mutations in one of the four genes; AGPAT2 (BSCL1), Seipin (BSCL2), CAV1 (BSCL3) and PTRF (polymerase I and transcript release factor)/Cavin (BSCL4), with majority of patients (~95%) studied thus far possessing mutations in BSCL1 or BSCL2. Here we will summarize the current knowledge on each of the causative genes, and focus on the mechanistic understanding of BSCL2 in this review. Here, BSCL2 is linked to Berardinelli-Seip congenital lipodystrophy.