CaseWA: Female, 5 yrs onset, French-Canadian
CasePresentingHPOs: HP:0002013, HP:0001944, HP:0001289, HP:0002367, HP:0001942, HP:0031962, HP:0001987, HP:0003236, HP:0001946, HP:0002919, HP:0000651, HP:0012120 (Vomiting, Dehydration, Confusion, Visual hallucinations, Metabolic acidosis, Elevated serum anion gap, Hyperammonemia, Elevated serum creatine kinase, Ketosis, Ketonuria, Diplopia, Methylmalonic aciduria)
HPOsFreeText: Low incorporation of 14C-propionate (4.1 nmol propionate/mg protein/18 h; control mean 10.8, SD 3.7) with no response to hydroxycobalamin
CaseNotHPOs: HP:0002151 (Increased serum lactate)
NotHPOsFreeText: N/A
CaseAddInfo: Parents are non-consanguineous with unremarkable family history, Treatment with carnitine and restricted protein intake normalized symptoms, Sequencing of the mother revealed Variant 2 without Variant 1 confirming compound heterozygosity
CasePreviousTesting: Metabolic acidosis values w/ elevated anion gap (pH = 6.96, bicarbonate 3.5 mmol/L and pCO2 15.9 mm Hg, anion gap 25.5 mmol/L); Mild hyperammonemia (107 μmol/L; ref. < 50); Elevated creatine kinase (from 498 IU/L initially up to 3062 IU/L, ref. < 150); Organic acid profiles were analyzed via gas chromatography–mass spectrometry with Table 1 showing relevant organic acid values; Proband was negative for propionyl-coA carboxylase deficency (811 pmol/min/mg protein with control mean 1123, PCCA and PCCB variants were negative) and ruled out MUT/cobalamin issues as well; Fusion experiments showed negative results for mut, cblA, and cblB complementation but no increase in activity when fused with MCEE confirming the pathway blockage
CaseGenotypingMethod: Extracted DNA from blood was amplified and three coding exons/splice site junctions of MCEE were Sanger sequenced. A deletion/duplicaiton analysis yeilded normal results. To search for an intronic sequence variant, total RNA was extracted and reverse-transcribed to confirm a 92-bp insertion between Exons 2 and 3. Resulting sequencing of this genomic area revealed a deep intronic variant that created a new consensus donor splice site that leads to a premature stop codon.
Variant1: NM_032601.4(MCEE):c.139C>T (p.Arg47Ter)
ClinVar: 2343, http://www.ncbi.nlm.nih.gov/clinvar/variation/2343
gnomAD: 0.0004884, https://gnomad.broadinstitute.org/variant/2-71351575-G-A
Variant2: NM_032601.3:c.379-644A>G
CAID: CA892631472, http://reg.clinicalgenome.org/redmine/projects/registry/genboree_registry/by_caid?caid=CA892631472
gnomAD: Not in gnomAD