Infantile lipid storage myopathy with nocturnal hypoventilation shows abnormal low-affinity muscle carnitine uptake in vitro

An infant with respiratory insufficiency, cardiomyopathy, lipid storage myo pathy and low muscle carnitine was diagnosed as having 'Ondine's curse' bec ause of recurrent nocturnal hypoventilation. Carnitine uptake was studied i n 20-day-old cultured muscle, where two distinct saturable transport compon ents are recognized: the high- and low-affinity-uptake. Experimental eviden ce suggests that low-affinity-uptake is muscle-specific, operating at physi ological carnitine concentration. In the patient's cultured myotubes, the l ow-affinity-uptake K-m was 260% of controls (P < 0.01), whereas kinetic par ameters of high-affinity uptake were normal. The high K-m indicates an imma ture or altered carnitine muscle carrier, which may decrease the physiologi c carnitine uptake. (C) 1999 Elsevier Science B.V. All rights reserved.