Homozygous loss-of-function mutations in PTF1A have been reported in 4 cases with a severe phenotype of pancreatic agenesis, resulting in permanent neonatal diabetes (PNDM) and pancreatic exocrine dysfunction, and a severe neurological phenotype with developmental delay, central hypoventilation, and complete cerebellar agenesis associated with a survival period of up to 4 months (3-5). Here, PTF1A is linked to isolated cerebellar hypoplasia/agenesis.