Table 1 Diagnostic evaluation in a patient with MARS mutations

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