A number of important mechanisms have been identified by which viruses can provoke asthma. From the data available, there does not appear to be one single mechanism available to explain virus-induced asthma. The relationship between viral URIs and asthma is complex and involves many organ systems: airway epithelium, autonomic nervous system control, and the immediate hypersensitivity system. Identifying the effects of respiratory viruses on airway function remains an important undertaking as we try to better understand and control this precipitant of asthma.

Ca2+ ions are critical to the functions of the various cells involved in the pathogenesis of asthma. Interest has developed regarding the potential use of Ca2+ antagonists in the management of asthma and allergic diseases. The information accumulated to date suggests that Ca2+ entry blockers may decrease airway smooth muscle responses to contractile agonists and may also reduce chemical mediator release from mast cells. Both processes would be expected to modify favorably the pathophysiology of asthma. This seems to have been demonstrated with the findings that certain Ca2+ entry blockers may inhibit exercise-induced bronchospasm and cold air- and antigen-induced airway narrowing. In several but not all experiments a direct bronchodilating effect of nifedipine was found in some subjects. In asthmatic patients with coexistent cardiovascular disease requiring beta-blocker therapy, it would be appropriate to use drugs such as the currently available Ca2+ entry blockers in place of the contraindicated beta-blocking agents. It appears that the currently available Ca2+ entry blockers have not provided a breakthrough class of therapeutic agents for the treatment of asthma. However, it seems highly likely that new Ca2+ antagonist drugs can be expected which will have greater specificity for airway smooth muscle and perhaps other cell types involved in the pathogenesis of asthma.

There is no solid evidence that pregnancy has an adverse effect on tuberculosis. With early diagnosis and prompt, adequate chemotherapy, the outcome of pregnancy in a woman with tuberculosis is likely to be good. Routine therapeutic abortion is not indicated. Data in the literature do not support the notion that pregnancy is a major risk factor for the development of tuberculosis, although no well-designed studies have been conducted. Screening of pregnant patients for tuberculosis should be based on consideration of other proved risk factors not on the fact of pregnancy. Preventive therapy should be given during the second and third trimesters of pregnancy to selected patients at high risk of progressive disease developing. Treatment of disease should be instituted promptly when disease is detected. The preferred regimens are INH-EMB, INH-RIF, or INH-EMB-RIF, although other drugs may be needed if the disease is recurrent or if there is resistance to these primary drugs. Mothers taking antituberculosis drugs can nurse their infants with little risk. With proper medical management, both tuberculosis and pregnancy can be expected to reach a happy conclusion in virtually all cases.

Cystic fibrosis is the most common fatal inherited disease of Caucasians. At present, cystic fibrosis accounts for most cases of chronic progressive pulmonary disease and for many other clinical features in the first three decades of life. Thus, it is a challenge to both pediatricians and internists, particularly chest physicians. The diagnosis is based on the triad of chronic obstructive pulmonary disease, pancreatic insufficiency, and increased levels of electrolytes in the sweat. The cardinal test for confirmation of the diagnosis is the "sweat test," which is an excellent discriminant for cystic fibrosis, even in adults. Ancillary features of cystic fibrosis may be of diagnostic assistance (eg, nasal polyposis, Pseudomonas aeruginosa in sputum, azoospermia, and others). Treatment of the pulmonary disease must be emphasized. Choice of antibiotics should be based on the results of sputum culture, but P aeruginosa is the most common pathogen. Removal of secretions by regular postural drainage and percussion is an integral part of the program. Pneumothorax, massive hemoptysis, cor pulmonale, and other complications may be encountered. Sinusitis is almost universal, and nasal polyposis is frequently present. Pancreatic insufficiency occurs in over 80 percent of the patients with cystic fibrosis and may result in intestinal malabsorption. Massive salt loss through the sweat in hot weather, a distinctive type of biliary cirrhosis without jaundice, gallbladder abnormalities, cholelithiasis, and diabetes mellitus also may be found. Of special importance are intestinal obstructive complications (meconium ileus in newborn infants with cystic fibrosis and intestinal obstruction due to fecal accumulation or intussusception in adults). Azoospermia is present in 95 percent of men and there is reduced fertility in women; however, pregnancy does occur in cystic fibrosis. This chronic and ultimately fatal disease produces a predictable set of psychosocial complications.