Slow onset fatal asthma — Based on clinical and pathologic observations, it has been estimated that approximately 80 to 85 percent of patients who die of asthma have a history of progressive symptoms for more than 12 hours and often for one to three weeks. At autopsy, the airways of patients who die of this "slow-onset" asthma typically feature an eosinophilic inflammation and obstruction of airway lumens by tenacious mucus and desquamated epithelium [17-19]. These changes probably develop over days to weeks. This suggests that most of these patients would have had sufficient time to seek medical attention for worsening shortness of breath [20,21].
Rapid onset fatal asthma — In a minority of patients with fatal or near-fatal exacerbations of asthma, possibly up to 20 percent (8 to 14 percent of asthma exacerbations in general), death occurs less than 2 to 6 hours after symptom onset [22-24]. The airways of these patients with "rapid-onset" fatal asthma do not have eosinophil-predominant inflammation or widespread mucus plugging typical of status asthmaticus. Instead, severe airway obstruction appears to be mainly due to smooth muscle bronchospasm and neutrophils are the predominant inflammatory cell in the airway mucosa.
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