Combined Respiratory Chain Deficiency and UQCC2 Mutations in Neonatal Encephalomyopathy: Defective Supercomplex Assembly in Complex III Deficiencies

Table 2

Clinical features of complex III deficiencies.

	Complex III subunits					Complex III assembly factors
Gene	MT-CYB	CYC1	UQCRB	UQCRC2	UQCRQ	UQCC2	UQCC2	UQCC3	TTC19	LYRM7	BCS1L
MIM accession	516020	615453	615158	615160	615159	615824	615824	616097	615157	615838	124000
Number of patients	>50	1	1	4	25, 1 kindred	1	1, this study	1	Ca. 15	9	>30
Onset	Childhood, adulthood	Infancy, early childhood	Late infancy	Neonatal	First months of life	Intrauterine	Intrauterine	Birth	Late infancy, adulthood	Infancy, 14 years	First years, infancy
Intrauterine growth retardation						Yes	Yes
Hearing impairment						Yes	n.a.	No			Yes
Hypotonia	Yes					Yes	Yes	Yes		Yes	Yes
Seizures						Yes	Yes	No			Yes
Abnormal EEG							Yes				Yes
Metabolic crisis			Yes					Yes		Yes
Lactic acidosis	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes		Yes	Yes
Increased CSF lactate	Yes					Yes
Hypoglycaemia		Yes	Yes	Yes				Yes
Developmental disability		No	No	No		No	n.a.	Yes	Yes	Yes	Yes
Intellectual disability		No	No	Yes (1)/no (1)	Yes		n.a.	Yes		Yes	Yes
Other features		In one hyperammonemic liver failure			Extrapyramidal movement disorder, survival into thirties	Renal tubular acidosis, no information after 9 years of age	Status epilepticus, died at 33 days of life	Muscular weakness	Later regression with spasticity and movement disorder leading to minimal residual state	Deterioration after metabolic crises, specific MRI pattern (multifocal cavitating leukoencephalopathy)	Hepatopathy, renal involvement, often early death