Table 1.

Diagnostic evaluation in a patient with MARS mutations

Disorders investigated	Investigations performed (normal unless otherwise indicated)
General investigations	• Serology for Hepatitis B, C, EBV, CMV; PCR for HIV
	• Alpha-1-antitrypsin and Pi type
	• Sweat test
	• Chromosomal microarray analysis: Paternally inherited duplication of 3p14.2 (616 kb) including C3orf67
	• Immunoglobulin levels, neutrophil oxidative burst activity, lymphocyte subpopulations
Disorders of intermediary metabolism	• Glucose, creatine kinase
	• Serum amino acids including homocysteine
	• Urine organic acids (including succinylacetone)(during liver failure, tyrosine metabolites but not succinylacetone observed)
	• Serum ceruloplasmin, serum and urine copper
	• Serum iron profile: Iron 65 μg/dl (nl 50-120); iron binding capacity, unsaturated <20 μg/dl (nl 100-400), iron binding capacity total 40 μg/dl (nl 250-450), transferrin saturation 162% (nl 10-45); ferritin 1053 ng/ml (nl 50-200)
	• Galactosemia metabolic panel (GALT, Gal-1 PO4 levels and DNA testing)
	• Acylcarnitine profile
Disorders of energy metabolism	• Glucose profiling; lactate 3.4 mmol/L (nl 0.5-1.5), pyruvate 0.32 mmol/L (nl 0.03-0.08); CSF lactate 3.5, CSF pyruvate 0.19
	• Muscle biopsy: histology, histochemistry, electron microscopy, respiratory chain enzyme analysis, muscle mtDNA content, mtDNA analysis for deletions and rearrangements, mtDNA sequencing
	• Muscle biopsy: excess of type IIC muscle fibers, immunostaining for succinate dehydrogenase and cytochrome c oxidase normal, normal mitochondrial appearance by electron microscopy
	• DGUOK, MPV17, and POLG1 sequencing
	• Ornithine decarbamylase gene sequencing
	• Liver biopsy: cholestasis, steatosis, bridging necrosis, minimal fibrosis, hemosiderin laden macrophages in the portal tracts, and normal appearing mitochondria and electron microscopy (Figure 1B-C), liver respiratory chain analysis, liver mtDNA content
	• Urine sugar and polyol and plasma sterol analyses
	• Initial aminoaciduria resolved
	• BCS1L sequencing for GRACILE (growth retardation, aminoaciduria, cholestasis, iron overload, lactacidosis, and early death) syndrome
	• Ophthalmology and cardiology assessments
	• MRI and CT scan of brain
Disorders of complex molecules	• Isoelectric focusing consistent with liver failure
	• White cell lysosomal enzyme screen
	• Wolman disease (lysosomal acid lipase deficiency)
	• Lysinuric protein intolerance (SLC7A7)
	• Urine mucopolysaccharides and oligosaccharides
	• Niemann-Pick types A and B (sphingomyelinase deficiency), and C (fibroblasts), GM1 gangliosidosis, and Gaucher disease
	• Bone marrow aspirate: RBC maturation arrest (precursors but not mature RBCs present); normal 5’nucleotidase
	• Plasma very long chain fatty acid analysis
	• Plasma and urine bile acid analysis, plasma cholesterol