Although these diseases -which include Friedreich's ataxia (FRDA), ISCU myopathy, a rare form of sideroblastic anemia, an encephalomyopathy caused by dysfunction of respiratory chain complex I and multiple mitochondrial dysfunctions syndrome - affect different tissues, a feature common to many of them is that mitochondrial iron overload develops as a secondary consequence of a defect in Fe-S cluster biogenesis.
Recently, the spectrum of diseases attributable to abnormal Fe-S cluster biogenesis has extended beyond Friedreich ataxia to include a sideroblastic anemia with deficiency of glutaredoxin 5 and a myopathy associated with a deficiency of a Fe-S cluster assembly scaffold protein, ISCU.