SLC25A20 and hyperinsulinemic hypoglycemia, familial, 4: In our study, CACT deficiency due to the c.199–10T > G variation is a severe phenotype with a significantly higher mortality, arrhythmia, seizures, and hyperammonemia incidence than other variations, while CACT deficiency caused by the c.82G > T mutation is associated with milder phenotype (5).