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AND THE ANSWER IS . . .
Discussion Recurrent dry cough is common in persistent asthma. In a minority of such cases of asthma, there is no associated wheeze noted by the patient. However, in a careful physical exam, an end-expiratory wheeze may be noted during the latter part of the forced expiratory maneuver. The presence of reversible expiratory obstruction, found during spirometry, suggests that "cough-equivalent" asthma is present. Occasionally, the usual spirometry may be within normal limits but there is evidence of airways hyper responsiveness, as detected by an inhalation challenge tests using methacholine or adenosine. The chronic dry cough associated with post-nasal discharge (PND) is likely not due to upper airway secretions reaching the bronchi. Rather, the cough is triggered when the PND hits sensitive areas in the hypo pharynx/peri-laryngeal areas. It was formerly thought that pertussis (Pert) was a disease limited to childhood, manifest as "whooping cough." There is now evidence that Pert infection is not rare in adults and is likely responsible for 10-20% of chronic dry cough in adults. The typical "whoop" is usually absent in such adult cases. It is though that Pert infects adults who never received the Pert vaccine in childhood or in whom protective immunity induced by the older whole cell Pert vaccine had waned. A chronic dry cough may be due very occasionally to a psychogenic cause. However, this appears to be a relatively rare event. Irwin et al state that psychogenic causes should be considered only after other possible causes have been ruled out. References |