Table 1.

Genetic, Biochemical, and Clinical Findings in Individuals with ELAC2 Mutations

ID	Sex		OXPHOS Activities and RNA Processing
		ELAC2 Mutations	RCC	% of Lowest Control	Absolute Values	Reference Range	Mean x-Fold Accumulation of Unprocessed RNA Intermediates		Clinical Features
		cDNA (NM_018127.6) and Protein (NP_060597)					Muscle	Fibroblasts	AO	Course	HCM	Other Features
#61525a	male	c.[631C>T; 1559C>T], p.[Arg211∗; Thr520Ile]			NA		NA	NA	4 months	death at 6 months	yes	intrauterine growth retardation, lactic acidosis, myocardial damage and necrosis associated with acute cardiac failure
#57415a,b	male	c.[631C>T; 1559C>T], p.[Arg211∗; Thr520Ile]	I II II+III IV	50% normal normal normal	0.07 0.29 0.46 1.07	(0.14–0.35) (0.18–0.41) (0.30–0.67) (0.91–2.24)	167	10.6	3 months	alive at 2 years, 10 months	yes	psychomotor and growth retardation, muscular hypotonia, microcephaly, dysphagia, lactic acidosis, sensorineural hearing impairment, hyperintensities in basal ganglia at age 3 months
#61982b	female	c.[460T>C; 460T>C], p.[Phe154Leu; Phe154Leu]	I II II+III IV	60% ND normal normal	0.062 ND 0.085 0.021	(0.104–0.268) ND (0.040–0.204) (0.014–0.034)	NA	10.5	2 months	death at 11 months	yes	intrauterine growth retardation, lactic acidosis, cardiac failure, normal muscle biopsy findings
#36355a	female	c.[1267C>T; 1267C>T], p.[Leu423Phe; Leu423Phe]	I II II+III IV	82% ND 100% 78%	0.14 ND 0.08 0.70	(0.17–0.56) ND (0.08–0.45) (0.90–4.70)	NA	NA	5 months	alive at 13 years	yes	mild psychomotor delay, muscular hypotonia
#65937a	female	c.[1267C>T; 1267C>T], p.[Leu423Phe; Leu423Phe]	I II II+III IV	86% 100% normal normal	0.12 0.18 0.32 1.61	(0.14–0.35) (0.18–0.41) (0.30–0.67) (0.91–2.24)	30	2.6	5 months	death at 4 years, 9 months	yes later DCM	psychomotor retardation, muscular hypotonia, cardiac failure, COX-deficient fibers

Mitochondrial respiratory chain complexes (RCC) in muscle: I, NADH-CoQ-oxidoreductase; II, succinate dehydrogenase; II+III, succinate cytochrome c oxidoreductase; IV/COX, cytochrome c oxidase. Enzyme activities were determined in muscle biopsies and normalized to citrate synthase (CS). Absolute values and reference ranges are given in [mU/mU CS]. Abbreviations are as follows: AO, age of onset; HCM, hypertrophic cardiomyopathy; DCM, dilated cardiomyopathy; NA, no material available; ND, not determined.

^aThese individuals are siblings.

^bInvestigated by exome sequencing.