The evidence is a bit more confusing when it comes to histologybased
searches for the disease mechanism in autopsy findings. Two
studies did find evidence of either increased mast cell counts or extracellular
tryptase in AFE patients compared with pregnant women with
traumatic death.18,36 These results are hard to reconcile with the unimpressive
serum findings of tryptase since presumably elevated circulating
levels of histamine would be created for systemic effects beyond the
lungs.