High serum serotonin in sudden infant death syndrome

Significance Sudden infant death syndrome (SIDS), the leading cause of postneonatal infant mortality, is defined as the sudden death of an infant less than 1 y of age that remains unexplained after a complete autopsy and death scene investigation. Although SIDS has been associated with deficiencies in central (brainstem) serotonin (5-hydroxytryptamine, 5-HT), there are no known peripheral biomarkers for SIDS. Here we demonstrate increased serum serotonin levels in a subset (31%) of SIDS infants compared with control infants. These findings suggest the potential of a high serum serotonin level as a forensic biomarker at autopsy to differentiate SIDS deaths with serotonergic defects from other causes of sudden death and, importantly, as evidence of a peripheral 5-HT abnormality in SIDS.