Moreover, hyperplasia and hypertrophy of PNEC/NEB occur within the lungs of infants classified as SIDS41 and there is a novel population of PNECs (as defined by the marker TUBB3) in lungs of SIDS cases with high serum 5-HT compared to that in SIDS cases with normal serum 5-HT42. This evidence concerns the gene TUBB3 and sudden infant death syndrome.