Need for strict clinical management of patients with carnitine palmitoyltransferase II deficiency: Experience with two cases detected by expanded newborn screening.

In Japan, carnitine palmitoyltransferase II (CPTII) deficiency has been included as one of the primary target diseases in the expanded newborn mass screening program since 2018. However, many cases of the severe infantile hepatocardiomuscular form of CPTII deficiency showed severe neurodevelopmental delay or sudden death, which indicated that management of CPTII deficiency in the acute phase remains to be studied in detail. Herein, we discuss two cases diagnosed by newborn mass screening. Patient 1 was under strict clinical management from the neonatal period, with >20 admissions in 14 months, while Patient 2 was managed using a relatively relaxed approach, with only 2 admissions in the same period. Patient 1 showed normal development; however, Patient 2 expired at the age of 1 year 2 months. To develop strategies for preventing sudden deaths in patients with CPTII deficiency, this retrospective study focused on detailed clinical management practices and biochemical findings during the acute phase. We also investigated the correlation between conventional biomarkers (such as creatine kinase) and long-chain acylcarnitines. We propose that strict monitoring and immediate medical attention, even in case of slight fever or minor abdominal symptoms, can help prevent sudden death in patients with CPTII deficiency. Considering the higher morbidity rate of such patients, strict and acute management of CPTII deficiency cannot be overemphasized.