Hydroxylated acylcarnitine can be elevated in newborns with carnitine acylcarnitine transporter deficiency

Mari Mori, MD, MS, Ashley S. Naughton, MD, Briana Scott, MD, Queenie Tan, MD, PhD, Surekha Pendyal, MSc, MEd, RD, Sarah P. Young, PhD, Loren Pena, MD, PhD

Duke University Medical Center, North Carolina, United States

Corresponding Author contact information: Mari Mori; phone 919-613-8313; email mari.mori@duke.edu

Abstract:

Carnitine acylcarnitine transporter (CACT) deficiency is a rare autosomal recessive fatty acid oxidation disorder. To date, 61 cases have been reported worldwide, mostly before the advent of expanded newborn screening. We report a term infant, firstborn to parents of Asian origin, with non-ketotic hypoglycemia, bradycardia, poor cardiac contractility, hyperammonemia, coagulopathy, and rhabdomyolysis at day of life 3. Ketone bodies, propionylglycine, and methylmalonic aciduria were not present in urine organic acid profile; however, there were medium chain dicarboxylic acids suggestive of fatty acid oxidation defect. Plasma amino acid profile was not consistent with a urea cycle defect.

Newborn screening and plasma acylcarnitine profile had elevations of long-chain saturated, unsaturated, and hydroxylated species including C16-OH. Based on these biochemical results, the patient was provisionally diagnosed with either long-chain 3-hydroxyacyl-CoA dehydrogenase or mitochondrial trifunctional protein deficiency (Tables 1 and 2).

The patient’s cardiac issues and biochemical abnormalities responded to aggressive glucose infusion, carnitine supplement, and she was discharged on predominantly medium chain triglycerides-containing formula mixed with canola oil to supplement essential fatty acid, and carnitine supplement. No mutations were detected on the HADHA or HADHB genes. Molecular testing confirmed CACT deficiency based on in heterozygous pathogenic mutations c.199-2A>C and c.199-10T>G in trans in the SLC25A20 encoding CACT. The infant, now 5 month-old, has had episodes of hyperammonemia during intercurrent illnesses. Gastric tube placement is planned due to poor feeding and weight gain.

Our case demonstrates that in CACT deficiency, hydroxylated acylcarnitines can be elevated, along with long chain acylcarnitines.

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