Iron overload has been detected in several diseases associated with mutations in proteins involved in the FeS proteins biogenesis [27], such as Friedreich ataxia [28–30], ISCU2 myopathy [31], GLRX5-related disease [32] and, more recently, in a neuromuscular disorder caused by a loss-of-function mutation in CIAO1, a key component of the cytosolic FeS clusters assembly complex [33]. Here, FES is linked to Tangier disease.