Primary carnitine (OCTN2) deficiency without neonatal carnitine deficiency

Although the diagnosis of a primary carnitine deficiency is usually based on a very low level of free and total carnitine (free carnitine: 1–5 μM, normal 20–55 μM) (Longo et al. 2006), we detected a patient via newborn screening with a total carnitine level 67 % of the normal value. At the age of 1 year, after interruption of carnitine supplementation for a 4-week period the carnitine profile was assessed and the free carnitine level had dropped to 10.4 μmol/l (normal: 20–55 μM) and total carnitine level had dropped to 12.7 μmol/l (normal: 25–65 μM). Transient carnitine deficiency was not likely anymore and DNA mutation analysis of the OCTN2 (SLC22A5) gene showed a homozygous c.136C>T (p.P46S) mutation, confirming the diagnosis of primary carnitine deficiency. We would like to emphasize that neonates with a primary carnitine deficiency might present with relatively high levels of total carnitine due to placental carnitine transfer, and also draw the attention to the importance of regular follow-up and the significance of genetic diagnostics in patients with a nonclassical presentation.