Missed Newborn Screening Case of Carnitine Palmitoyltransferase-II Deficiency
Carnitine palmitoyltransferase-II (CPT-II) deficiency can be detected through newborn screening with tandem mass spectrometry. We report a 4-year-old patient with rhabdomyolysis due to CPT-II deficiency, which was initially missed by newborn screening. The patient presented with a 2-day history of fevers, upper respiratory infection, diffuse myalgia, and tea-colored urine. Her medical history was notable for frequent diffuse myalgia when ill. She was demonstrated to have homozygous mutation c.338C>T, p. S113L in CPT2, which is typically found in the adult-onset, myopathic form of the disease. An unknown number of CPT-II deficient patients with normal newborn screening have not yet presented to medical care with the adult-onset, myopathic form of disease. We conclude that (1) not all cases of CPT-II deficiency are currently detected through newborn screening, even when blood is appropriately collected on day 2 of life and (2) CPT-II deficiency should be kept on the differential for patients presenting with rhabdomyolysis, even if the newborn screening results were normal.
The authors thank Kathryn Kadash-Edmondson for critical reading of the manuscript and Rebecca Ganetzky, MD, for help with R4S analysis.
The authors also thank Piero Rinaldo, MD, PhD, Mayo Clinic, for his assistance in the preparation of the figures and for granting permission to reproduce material from the R4S and CLIR websites.
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