Case53: 4 mo (at biopsy), Arab/Turkish, female

CaseNotHPOs: metabolic acidosis, homocystinuria (HP:0001942, HP:0002156)

NotHPOsFreeText: normal synthesis of adenosylcobalamin and methylcobalmin (suggests patient does not have cblX disease).

Case 53 (Level 2)

CasePreviousTesting: same as group. found 1.0 nmol/mg protein/18 h propionate incorporation, 0.8 nmol/mg/protein/18 h propionate incorporation with hydroxocobalamin supplementation

CaseMethod1: same as group

CaseMethod2: same as group

CaseGenotypingMethod: same as group

Variant1: NM_005334.2:c.4475C>T (p.Pro1492Leu)

ClinVar: n/a

CAID: CA415114585

gnomAD: n/a

CaseAddInfo: Originally identified as mut0 type patient through somatic cell complementation. But NGS instead identified a novel heterozygous mutation in HCFC1, which is detailed above. Based on clinical presentation it was determined unlikely that the identified variant is related to the patients MMA.