Involvement of mast cells in sudden infant death syndrome.

The pathogenesis of sudden infant death syndrome (SIDS) is elusive and probably multifactorial. The occurrence of mast cell activation in SIDS was assessed in this study by measuring concentrations of tryptase, a neutral protease produced mainly by mast cells, in postmortem sera from term infants with SIDS and from age-matched control infants who died unexpectedly at home from a known cause. Tryptase levels were significantly higher in the 50 infants with SIDS than in the 15 control infants (p = 0.0004). Forty percent of the infants with SIDS and none of the control infants had a tryptase level greater than 10 ng/ml, the threshold chosen to indicate premortem mast cell activation. An infant with SIDS had a 20-fold higher chance of having an elevated tryptase level compared with a control infant. The postmortem interval did not influence these results. Thus mast cell-mediated anaphylaxis is likely to be the pathogenetic mechanism involved in some but not all SIDS cases. Recognition of this pathway as operative in SIDS should facilitate a more precise identification of the allergens involved, the processes leading to mast cell activation, and procedures to identify those infants at risk for anaphylaxis, and should, in time, lead to better therapeutic interventions aimed at preventing this specific cause of SIDS.