Sudden infant death syndrome: pathology and pathophysiology

Sudden infant death syndrome is the most common cause of infant death between the ages of 1 week and 1 year of age and accounts for approximately 50 percent of the deaths of infants between the ages of 2 and 4 months. The unique age distribution and its relationship to sleep particularly characterize SIDS; however, there are other factors, such as maternal smoking, male sex, prematurity or low birth weight, which place an infant at higher risk of SIDS. Intrathoracic petechiae with characteristic microscopic topography are the most frequent pathologic finding. However, pulmonary congestive edema and minor microscopic inflammatory infiltrates are often seen. Stenotic lesions within the coronary arteries supplying the conduction system have been identified in a few SIDS victims; however, current evidence favors respiratory dysfunction as the primary mechanism of death in most SIDS babies. Based upon pathologic, experimental, and clinical observations, an argument can be made that upper airway obstruction, e.g., secondary to obstructive sleep apnea, is one, if not a common, cause of death in SIDS. There are cases in which subtle morphologic evidence suggests SIDS represents the termination of a chronic hypoxic/hypoxemic disorder such as recurrent apnea.