The carotid bodies of four infants who died of sudden infant death syndrome (SIDS) were compared, using electron microscopic techniques, with the carotid bodies of various control subjects. In the SIDS patients, there was a marked reduction or absence of the dense cytoplasmic granules of the carotid chemoreceptor cells, as well as a reduction in cell number and size. These ultrastructural abnormalities may be pathophysiologically related to SIDS. A defect in this respiratory control organ could block normal stimulation of respiration during the periods of hypoxia that occur during episodes of sleep apnea in infancy. Further studies by electron microscopy are required to confirm degranulation of the carotid body as a pathognomonic sign of SIDS. Screening of high-risk infants should be directed at studying the carotid body and its mediated responses to hypoxia.
