The diagnosis of amniotic fluid embolism: an immunohistochemical study for the quantification of pulmonary mast cell tryptase

Recent clinical articles have suggested that amniotic fluid embolism (AFE) may be the result of anaphylactic reactions to fetal antigens and that the major part of this clinical syndrome is the result of mast cell degranulation and of the release of histamine, tryptase and other mediators. Tryptase, a neutral protease, is known to be the dominant protein component of the secretory granules of T and TC mast cells. In this paper we have examined the presence and the pulmonary distribution of mast cell tryptase utilizing specific immunohistochemical studies and morphometric evaluation in six cases of fatal amniotic fluid embolism compared to six subjects who died following anaphylactic shock and two control groups (five and six cases respectively) of traumatic death. The results demonstrate a numerical increase of pulmonary mast cells in the subjects who died of AFE (average cell number 54.095) with values corresponding to those encountered in cases of death due to anaphylactic shock (average cell number 51.378) compared with that of the traumatic control groups (average cell number 24.477 and 9.995 respectively). These results can shed light on additional criteria for the diagnosis of amniotic fluid embolism.