Case 1 was a 20-year-old man with MMA. He was born via cesarean section because of placenta previa at gestational age of 37 weeks with birth weight of 2.7 kg. Due to positive family history (his brother had MMA), he underwent metabolic investigation. His metabolic evaluation revealed blood ammonia level of 400–500 mg/dL and elevated C3 carnitine level (48.8; reference range, < 4.1). The methylmalonic acid level in urine was 1617 µg/mg Cr, and elevation in plasma glycine (415 µmol/L) and alanine (978 µmol/L) levels were noted. Cobalamin (Cbl) incorporation study of 14C-propionate showed lack of response to Cbl (i.e. mut0) and slightly low response to adocobalamin (AdoCbl). Molecular investigations revealed a compound heterozygous c.1105C > T(p.R369C), p.G94Q mutation. He was fed with special formula (Propiomex), regular infant formula, low-protein food, and L-carnitine supplement (100 mg/kg/d). His developmental evaluation at 20 months of age showed a mild delay. Prior to 5 years of age, blood urea nitrogen (BUN) and creatinine were in the normal range (BUN 6.6–12.3 mg/dL /creatinine 0.7–0.8 mg/dL). However, after 5.5 years of age, his renal function slowly deteriorated, showing a BUN level of 16.2–29.2 and creatinine level of 0.81–1.02. He was hospitalized multiple times due to metabolic decompensations (acidosis, dehydration, and hyperammonemia) after trivial infections or skipping of the special formula. At 6 years of age, his eye sight deteriorated progressively and he became legally blind due to optic atrophy by 10 years of age. He received growth hormone treatment for metabolic induction to anabolism and improvement of his short stature. At 15 years of age, he experienced vomiting and abdominal pain due to pancreatitis. His metabolic status became unstable; he was hospitalized more than 7 times with pancreatitis (Table ). At this time, he began to experience hand tremors due to his metabolic condition. After recurrent pancreatitis at 19 years of age, he showed glucose intolerance. By the age of 20 years, he developed DM, requiring insulin injection. His most recent metabolic crisis was accompanied by severe metabolic acidosis (pH 6.8), liver dysfunction (aspartate aminotransferase (AST) 245 IU/L, alanine aminotransferase (ALT) 316 IU/L), hyperventilation, hemorrhagic gastritis, and left pleural effusion. His pancreatic amylase and lipase levels were > 4000 U/L. He was put on continuous renal replacement therapy for 3 days. During the metabolic crisis, he experienced seizures and hand tremors, although the results of brain magnetic resonance imaging (MRI) and electroencephalogram (EEG) were normal. The abdominal computed tomography (CT) showed necrotizing pancreatitis and follow-up ultrasound after 1 month of pancreatitis showed a pancreatic pseudocyst. His renal function progressively deteriorated, showing a BUN level of 40.1–60 mg/dL, Cr level of 2.04–2.81 mg/dL, and estimated glomerular filtration rate (eGFR) level of 43.7 mL/min/1.73 m2. His metabolic parameters were as follows: pH, 7.30–7.31; HCO3 level, 11.2–20.6; methylmalonic acid level, 1768–3861 µg/mg Cr; glycine level, 625–1187 µmol/L (normal range: 158–302 µmol/L); alanine level, 508–825 µmol/L (normal range: 185–537 µmol/L). His ferritin levels were 280–581.53 ng/mL (normal range: 50–200 ng/mL). His current weight is 46.1 kg and height is 164 cm. He has recovered completely from pancreatitis, and his glucose levels are being controlled using insulin (Table ).
Case 3 was a 14-year-old boy. He was born via normal spontaneous vaginal delivery (NSVD) without complication at the gestational age of 36 weeks, with birth weight of 3.2 kg. C3 carnitine level elevation (37, reference: < 4.1) was detected in the expanded newborn screening program. His urine organic acid analysis confirmed PPA. His blood gas and blood ammonia levels were normal. The fibroblast carboxylase assay revealed reduced propionyl-CoA carboxylase (PCC) activity [9 pmol/min/mg protein (reference: > 91 pmol/min/mg)], normal methylcrotonyl-CoA carboxylase (MCC) activity [55 pmol/min/mg protein (reference: > 31 pmol/min/mg)], and normal pyruvate carboxylase (PC) activity [124 pmol/min/mg protein (reference: > 71)]. Propionyl carboxylase assay using biotin-supplemented culture medium showed that he was non-responsive to biotin. He was fed breast milk exclusively and an unrestricted normal regular diet. However, at 23 months of age, he was hospitalized for metabolic decompensation and hyperammonemia following rotavirus gastroenteritis. Special formula for PPA was introduced after that. The patient was not compliant with the PPA formula because of its taste. He was admitted to the hospital 12 times due to metabolic decompensation (i.e. metabolic acidosis and hyperammonemia) at 23 months of age. The unusual clinical presentation was recurrent headache, which was relieved by intravenous glucose/electrolyte infusion. At 13 years, he was diagnosed with Osgood-Schlatter disease. At 14 years of age, ophthalmologic evaluation revealed Avellino corneal dystrophy. He experienced diabetic ketoacidosis, which was associated with weight loss. His blood glucose level was 2018 mg/dL and C-peptide level was 0.87 ng/mL (reference: 0.81–3.86 ng/mL). His autoantibody profile was as follows: islet cell antibody (Ab)-negative, insulin Ab-negative, and anti-GAD Ab level < 0.11 (reference: ≤ 1.00 U/mL). Insulin was administered to the patient, after which he became compliant with the PPA special formula for diet control (Table ). His long-term metabolic profile revealed glycine level of 261–314 µmol/L (normal range: 158–302 µmol/L), significantly elevated glutamine level of 1169–1545 µmol/L (normal range: 360–740 µmol/L), and small amounts of 3-hydroxypropionic acid, propionyl glycine, and methyl citrate. His amylase level had always been normal at 81–90 U/L (reference: 28–100 U/L) during our long-term follow-up.