Fig. 7.26 Necrotizingenterocolitis.(A)Atpostmortemexaminationinaseverecase,theentiresmallbowelwasmarkedlydistendedandperilouslythin(usuallythisappearanceimpliesimpendingperforation).(B)Thecongestedportionoftheileumcorrespondstoareasofhemorrhagicinfarctionandtransmuralnecrosis.Submucosalgasbubbles(pneumatosisintestinalis)canbeseeninseveralareas(arrows).
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Table 7.7 Factors Associated With Sudden Infant Death Syndrome (SIDS)
Drugabuseineither parent,specificallypaternalmarijuanaandmaternalopiate,cocaineuse
Brainstemabnormalities,associatedwithdelayeddevelopmentofarousalandcardiorespiratorycontrol
Fattyacidoxidationdisorders(MCAD,LCHAD,SCHAD mutations) as respiratory drive, blood pressure, and upper airway reflexes. Abnormalities in serotonin-dependent signaling in the brain stem may be the underlying basis for SIDS in some infants.
Among the potential environmental causes, prone sleeping position, sleeping on soft surfaces, and thermal stress are possibly the most important modifiable risk factors for SIDS. Many studies have clearly shown increased risk for SIDS in infants who sleep in a prone position, prompting the American Academy of Pediatrics to recommend placing healthy infants on their backs when laying them down to sleep. This “Back to Sleep” campaign has resulted in substantial decreases in SIDS-related deaths since its inception in 1994. The prone position increases the infant’s vulnerability to one or more recognized noxious stimuli (hypoxia, hypercarbia, and thermal stress) during sleep. In addition, the prone position also is associated with decreased arousal responsiveness compared with the supine position.
Of note, SIDS is not the only cause of sudden unexpected death in infancy. Therefore, SIDS is a diagnosis of exclusion, requiring careful examination of the death scene and a complete postmortem examination. The latter can show an unsuspected cause of sudden death in as many as 20% or more of babies presumed to have died of SIDS (
Table 7.7 ). Infections (e.g., viral myocarditis or bronchopneumonia) are the most common causes of SUID, followed by a congenital anomaly. As a result of advancements in molecular diagnostics, several genetic causes of SUID have emerged. For example, fatty acid oxidation disorders, characterized by defects in mitochondrial fatty acid oxidative enzymes, may be responsible for as many as 5% of sudden deaths in infancy; of these, a deficiency in medium-chain acylcoenzyme A dehydrogenase is the most common. Retrospective analyses in cases of sudden infant death originally designated SIDS also have revealed mutations of cardiac sodium and potassium channels, which result in a form of cardiac arrhythmia characterized by prolonged QT intervals; these cases account for no more than 1% of SUIDs.
C4b)*SIDSisnottheonlycauseofSUIDs,butratherisadiagnosis of exclusion.Therefore, performanceofanautopsymayoftenshowfindingsthatwouldexplainthecauseofanSUID.Thesecasesshouldnot,strictlyspeaking,belabeledas“SIDS.”SCN5A, Sodiumchannel,voltage-gated,typeV,alphapolypeptide;KCNQ1, potassiumvoltage-gatedchannel,KQT-likesubfamily,member1;MCAD, medium-chainacylcoenzymeAdehydrogenase;LCHAD, long-chain3-hydroxyacylcoenzymeAdehydrogenase;SCHAD, short-chain3-hydroxyacylcoenzymeAdehydrogenase;MTCYB, mitochondrialcytochromeb;C4, complementcomponent4.