Table 1

Summary of the previously described mutations in COIII together with our new case

AA exchange	Position	Reference	Clinical picture	Onset	% Heteroplasmy	RRF	COX activity
F251L	T9957C missense	Manfredi et al⁹	MELAS	6 years	81% in muscle, 60% in blood	Few	Low to normal
Missing 94–98 (FAGFF)	15bp in frame deletion	Keightley et al⁴	Recurrent myoglobinuria	15 years	97% in muscle, 0.7% in blood	Several	14% residual activity
W249X	G9952A	Hanna et al⁵	Myoglubinuria, myopathy, encephalopathy	17 years	57% in muscle, 0% in blood	No	20% residual activity
Q111X	9537 insC	Tiranti et al¹⁰	Leigh-like syndrome	4 years	Virtually homoplasmic (muscle, fibroblasts, blood)	No	10% residual activity
W58X	G9379A	This paper	Myopathy	6 years	93% in muscle, 0% in blood	Numerous	9% residual activity