FXN deficiency in humans is at the core of the cardio- and neurodegenerative disorder Friedreich’s ataxia, a rare autosomal-recessive genetic disease typically caused by a trinucleotide repeat expansion in the first intron of the FXN gene; the expansion disrupts transcription of the gene and results in FXN deficiency [34]. This evidence concerns the gene FXN and hyperinsulinemic hypoglycemia, familial, 4.