Two SPINK1 knockouts, one a homozygous deletion of the entire SPINK1 gene, the other the homozygous insertion of a full-length inverted Alu element into the 3′-untranslated region of the SPINK1 gene (experimentally determined to cause the complete loss of SPINK1 expression), presented with severe exocrine pancreatic insufficiency around 5 months of age [53]. Here, SPINK1 is linked to exocrine pancreatic insufficiency.