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Table 4.

Complex III variants

Disease/clinical features	Variant	Subunit	AA change	Age^a	% VAF				Complex III		Reference
Disease/clinical features	Variant	Subunit	AA change	Age^a	Muscle	Blood	Fibroblasts	Other	Residual activity, %	Protein levels	Reference
MELAS	14864T > C	MT-CYB	Cys40Arg	15 yr	39	32	42	57, urinary sediment	72, muscle		(Emmanuele et al. 2013)
Mitochondrial disease	15150G > A	MT-CYB	Trp135X		60		0	0, lymphocytes	7, muscle 183, fibroblasts 56, lymphocytes	↓	(Legros et al. 2001)
Progressive EXIT	15170G > A	MT-CYB	Gly142X	40 yr	99		<1	<1, lymphocytes	10, muscle		(Bruno et al. 2003)
Mitochondrial disease	15197T > C	MT-CYB	Ser151Pro		80		0	0, lymphocytes	17, muscle^b 167, fibroblasts^b 72, lymphocytes^b	↓	(Legros et al. 2001)
Hypertrophic cardiomyopathy	15243G > A	MT-CYB	Gly166Glu	8 yr			100	90, heart	22, heart^b		(Valnot et al. 1999)
Severe growth restriction	15498G > A	MT-CYB	Gly251Asp	3 yr			100	100, lymphocytes	36, fibroblasts 43, lymphocytes		(Haut et al. 2004)
Asymptomatic	15498G > A	MT-CYB	Gly251Asp				100	100, lymphocytes	36, fibroblasts 57, lymphocytes		(Haut et al. 2004)
Asymptomatic	15498G > A	MT-CYB	Gly251Asp					100, lymphocytes	50, lymphocytes		(Haut et al. 2004)
Deafness, EXIT, cognitive dysfunction, and growth restriction	15579A > G	MT-CYB	Tyr278Cys	19 yr	88			15, leukocytes	6, muscle		(Wibrand et al. 2001)
Mitochondrial encephalopathy	15699G > C	MT-CYB	Arg318Pro	38 yr	88			16, urinary sediment13, lymphocytes14, hair shaft	4, muscle		(Blakely et al. 2005b)
Neonatal polyvisceral failure	15635T > C	MT-CYB	Ser297Pro	Newborn	100		100	100, leukocytes 100, liver	83, muscle 7, fibroblasts 66, liver		(Fragaki et al. 2009)
Progressive EXIT, muscle cramps and lactic acidosis	15800C > T	MT-CYB	Gln352X	24 yr	45			<1, “others”	27, muscle		(Lamantea et al. 2002)

[i] ^aAge of the patient at which the VAF and complex I activity were measured.

[ii] ^bNormalized to protein, not citrate synthase.

[iii] (AA) Amino acid; (VAF) variant allele frequency; (CYB) cytochrome b; (MELAS) mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes; and (EXIT) exercise intolerance.