Table 2

Diagnostic criteria in the 31 patients with proved mitochondrial disorders

Patient	Clinical syndrome	OXPHOS/PDH deficiency	Mt-DNA mutation	Muscle histopathology	Abnormal electron microscopy	Suggestive organic aciduria	Afflicted sibling
1	Leigh	Complex V	T8993G
2	Leigh	PDH E1
3	Leigh	Generalised
4	Leigh	Complex I				3-MGA
5	NARP		T8993G				Patient 6
6	NARP		T8993G				Patient 5
7	MiMyCa	Complex I		RRF	Yes
8	MiMyCa			RRF
9	Barth					3-MGA
10	LHON		3460
11	E3 deficiency	PDH E3
12	E3 deficiency	PDH E3
13	Costeff					3-MGA
14	Costeff					3-MGA	Patient 15
15	Costeff					3-MGA	Patient 16
16	Anaemia + myopathy	Complex I + IV			Yes
17	IPO + NB	Complex IV		No COX staining			Patients 18,19
18	IPO + NB						Patients 17,19
19	IPO + NB						Patients 17,18
20	Encephalopathy	Complex I
21	Encephalopathy	Complex I
22	Encephalopathy	Complex I					Patient 23
23	Encephalopathy						Patient 22
24	Encephalopathy	Complex I
25	Encephalopathy	Complex I + III + IV			Yes
26	Encephalopathy	Complex I
27	Encephalopathy	Complex I
28	Encephalopathy	Complex I			Yes
29	Encephalopathy	Complex II				3-MGA
30	Encephalopathy	Complex I
31	Encephalopathy	PDH E1 + generalised

Generalised refers to a generalised deficiency of all respiratory chain enzymes.
COX, cytochrome C oxidase (complex IV); IPO + NB, intestinal pseudo-obstruction and neurogenic bladder; LHON, Leber’s hereditary optic neuropathy; 3-MGA, 3-methylglutaconic aciduria; MiMyCa, maternally inherited myopathy and cardiomyopathy; Mt-DNA, mitochondrial DNA; NARP, neuropathy, ataxia, retinitis pigmentosa; PDH, pyruvate dehydrogenase; OXPHOS, oxidative phosphorylation or respiratory chain enzymes; RRF, ragged red muscle fibres.