Table 1.

Clinical and other features of patient cohort

	Patients with:
Clinical Diagnosis	mtDNA mutations	nuclear mutations	unknown mutations
Leigh Syndrome	11	6	15
Other mitochondrial encephalopathy	3	1	13
Cardiomyopathy/encephalopathy	0	2	12
LIMD	2	6a	9
MELAS	6	0	0
Mitochondrial myopathy	2	0	5
Mitochondrial cytopathy	1	0	3
Mitochondrial hepatopathy	0	3	2
VCFS/DiGeorge Plus	0	0	1
Total	25	18	60
Consanguinity	0	7	6
Family historyb: definite, possible	7, 9	9, 0	9, 9
Fibroblast defectc (# tested)	17 (20)	10 (15)	18 (32)

^a2 patients were affected prenatal diagnoses that were terminated and diagnosis was assumed to be the same as the proband.

^bFamily history consistent with a mitochondrial disorder

^cCI enzyme defect present in patient fibroblasts

Abbreviations: LIMD, Lethal Infantile Mitochondrial Disease; MELAS, Mitochondrial Encephalopathy, Lactic Acidosis, Stroke-like episodes; VCFS, Velo-Cardio-Facial Syndrome;