Table 1

Clinical and biochemical features of index patients and affected siblings

Pedigree	Patient ID number	Affected gene	Clinical diagnosis	CI/CS		Other features
Pedigree	Patient ID number	Affected gene	Clinical diagnosis	Muscle	Fibroblasts	Other features
MITO005	50845	NDUFB3 comp het	ME, MM	ND	21%^*/17%	Muscular hypotonia, developmental delay, lactic acidosis blood
MITO036	33463	NDUFS3 hom	ME, MM	28%	36%	Developmental delay, muscular hypotonia, lactic acidosis, rapid progress of disease
MITO004	33284	NDUFS8 comp het	ME, HCM	38%	52%	Muscular hypotonia, respiratory insufficiency
MITO021	33027	NDUFS8 hom	LS	8%	54%	Muscular hypotonia, dyskinesia, epilepsy, lactic acidosis, MRI changes
MITO021	44559	NDUFS8 hom	LS	ND	ND	Muscular hypotonia, lactic acidosis blood and CSF, MRI lesions basal ganglia and brainstem, hypertrophic cardiomyopathy
MITO053	59029	ACAD9 hom	HCM	3%	ND	Muscular hypotonia, lactic acidosis, exercise intolerance
MITO053	59033	ACAD9 hom	HCM	ND	ND	Muscular hypotonia, lactic acidosis, exercise intolerance
MITO053	59036	ACAD9 hom	HCM	ND	ND	Muscular hypotonia, lactic acidosis, exercise intolerance
MITO049	44409	MTFMT comp het	LS	16%	ND	Vertical gaze palsy, partial optic atrophy, mental retardation, tetra-spastic, neurosensoric bladder dysfunction
MITO061	61606	MTFMT hom.	LS	12%	ND	Developmental delay, muscular hypotonia, ataxia, MRI lesions basal ganglia, periventricular white matter, dorsal column
MITO028	33281	Unclear	ME	33%	49%	Developmental delay, muscular hypotonia, spastic tetraparesis, brain atrophy and demyelinisation,
MITO028	37800	Unclear	ME	ND	ND	Developmental delay, muscular hypotonia, spastic tetraparesis, seizures, brain atrophy, lactic acidosis
MITO038	46072	Unclear	ME, MM	4%	27%^*	Lactic acidosis, developmental delay, muscular hypotonia, ataxia, coarctation of aorta
MITO023	37796	Unclear	ME	19%	67%	Developmental delay, failure to thrive, muscular hypotonia, seizures, lactic acidosis

↵* Normalised to complex IV.
CI/CS, complex I activity normalised to citrate synthase in per cent of mean of >10 controls; comp het, compound heterozygous; CSF, cerebrospinal fluid; hom, homozygous; HCM, hypertrophic cardiomyopathy; LS, Leigh syndrome; ME, mitochondrial encephalopathy; MM, mitochondrial myopathy; ND, not determined.