Laryngeal basement membrane thickening is not a reliable postmortem markerfor SIDS - Results from the Chicago Infant Mortality Study

It has been suggested that laryngeal basement membrane (LBM) thickening is a pathognomonic postmortem marker for sudden infant death syndrome (SIDS) a nd is not seen in other causes of explained sudden infant death. To test th is hypothesis, we evaluated longitudinal sections of the right hemilarynx t aken through the midpoint of the true vocal cord from 129 SIDS cases and 77 postneonatal sudden infant death controls. Using a five-point semi-quantit ative scale, maximum LBM thickness (LBMT) for SIDS cases and controls was n ot statistically different (mean, 2.39 + 0.69 and 2.40 + 0.77, respectively ). Likewise, scores based on the average thickness along the entire basemen t membrane (i.e., "average" score), were not found to be different between SIDS cases and controls. Average and maximum LBMT increased with age in bot h SIDS cases and controls and were not different between SIDS cases and con trols within each age interval. Similar trends in the distribution of maxim um and average LBMTs were found between black and Hispanic SIDS and control s; the number of white/non-Hispanic infants was too low for meaningful comp arisons. Maximum and average LBMTs were not different in SIDS cases and con trols exposed to environmental tobacco compared with unexposed infants. The LBMTs also increased significantly with body weight and length in both SID S cases and controls. Finally, there were no differences in LBMT in infants intubated prior to death compared with those who were not intubated. From these data, we conclude that LBMT is not pathognomonic of SIDS, is present or absent with equal frequency in SIDS and controls, increases with postnat al age, and does not correlate with passive smoke exposure. Therefore, LBMT should not be used to diagnose SIDS.