Mitochondrial hepatopathy: Respiratory chain disorders- ‘breathing in and out of the liver’

Table 1 Various mitochondrial primary respiratory chain disorders

Disorder	Mutation/defective gene	Location of defect	Affected proteins/consequence
Neonatal liver failure: (1) Complex I deficiency; (2) Complex III deficiency; (3) Complex IV deficiency; and (4) Multiple complex deficiencies	ACAD9; BCS1L; SCO1	nuDNA	Respective complexes deficiency as per name
Delayed onset liver failure: Alper’s Huttenlocher syndrome	POLG mutation	nuDNA	Defective mtDNA polymerase; mtDNA depletion
MtDNA depletion syndrome	DGUOK; TK-2; MPV 17; POLG	All nuDNA	Decreased deoxyribonucleotide concentrations within mitochondria
Mitochondrial neuro-gastrointestinal encephalomyelopathy	TYMP	nuDNA	Markedly low levels of thymidine phosphorylase activity
Pearson marrow pancreas syndrome	4000-5000 bp deletions in mtDNA; tRNA gene of mtDNA	Both mtDNA	Complex I, IV, V
Navajo neurohepatopathy	MPV 17 mutations	nuDNA	mtDNA depletion
Villous atrophy with hepatic involvement	Rearrangement defect/deletion-duplications in mtDNA	mtDNA	Complex III deficiency

nuDNA: Nuclear DNA; mtDNA: Mitochondrial DNA.