In Reply.Dr Elpeleg correctly states that the metabolic workup for our surviving patients included only screening for urinary reducing substances and an amino acid profile. He states that this is inadequate for diagnosis of defects in mitochondrial β-oxidation of fatty acids, which has been reported to cause SIDS, and suggests that fibroblast culture be performed for all SIDS victims and patients with near-miss cases of SIDS.
The patients we reported were born between October 1985 and April 1990, or before the interesting study by Harpey et al1 was published. Still, it is unlikely that any of our patients had defects in fatty acid β-oxidation because (1) the illness did not progress in survivors, and (2) fatty infiltration of the liver was not present in SIDS victims. Fatty infiltration of the liver, heart, and skeletal muscle is the hallmark of this disorder. Losty et al2 reported an infant with medium-chain