PHYH and cardiac arrhythmia: Complementary tests for diagnosis include CSF analysis (increased protein levels without an increase in the number of cells present in the CSF), 24-h Holter monitoring (as increased incidence of arrhythmias is observed in this group of patients), and measurement of peroxisomal enzyme phytanoyl-CoA hydroxylase (which converts phytanic acid into α-hydroxyphytanic acid).98