PTF1A and permanent neonatal diabetes mellitus: PNDM is a genetically heterogeneous disorder due to mutations in 23 different genes described to date: KCNJ11, ABCC8, FOXP3, GCK, PDX1, pancreas-specific transcription factor 1A (PTF1A), EIF2AK3, SLC2A2, GATA6, GATA4, SLC19A2, WFS1, NEUROD1, NEUROG3, RFX6, LRBA, NKX2-2, MNX1, IER3IP1, INS, STAT3, GLIS3 and HNF1B (3,4,5,6,7,8,9).