Friedreich's ataxia: the vicious circle hypothesis revisited

Table 2 Cardinal clinical symptoms associated with deficiencies in frataxin, vitamin E, ABCB7 (mitochondrial iron overload), GLRX5 (impaired ISC synthesis) and ISCU (impaired ISC synthesis)^a

Clinical symptoms	Frataxin deficiency	Vitamin E deficiency	ABCB7 deficiency	GLRX5 deficiency	ISCU deficiency
Ataxia	+++	+++	+++	-	-
Cardiomyopathy	+	+	-	-	-
Diabetes mellitus	+	(+)	-	+	-
Myopathy	(+)	(+)	-	-	+++
Sideroblastic anaemia	-	-	+++	+++	-
Hepatosplenomegaly	-	-	-	++	-
Lactic acidosis	(+)	(+)	-	-	+++

^a+++: hallmark of the disease; ++: present in most cases; +: present only in a subset of patients or late in the course of the disease; (+): reported occasionally; -: usually absent. Disease symptoms shared with Friedreich's ataxia are represented using a similar grey colour.

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