[Unrecognized causes of chronic cough].

Chronic cough is defined as persistence of the symptom for longer than one month. It is a common reason for consultation. A systematic diagnostic approach based on the history, clinical examination and a number of investigations (chest x-ray, lung function tests, oesophageal pH monitoring and sinus x-rays) reveals the cause in most cases. The main aetiologies are post-nasal drip, gastro-oesophageal reflex, asthma, chronic bronchitis, and the use of angiotensin converting enzyme inhibitors. Nevertheless, in some cases, the cause is not found. In this situation it is necessary to search for less common pathologies where cough is just a symptom of systemic disease, such as connective tissue disorder (Sjogren's syndrome, atrophic polychondritis), vasculitis (Wegener's granulomatosis), Horton's syndrome (cluster headaches), amyloidosis and inflammatory bowel disease. It may also be a matter of local pathology of the tracheo-bronchial tree, such as tracheo-bronchomegaly, tracheopathia osteoplastica, rare or unrecognized infections (whooping cough, post-viral cough, bronchial tuberculosis), reactive bronchial dysfunction, eosinophilic bronchitis or radiologically occult bronchial carcinoma. Il is also necessary to consider vocal cord dysfunction and cough due to medication before accepting a diagnosis of psychogenic cough.