Correspondence

Acute Chest Syndrome in Sickle Cell Disease

N Engl J Med 2000; 343:1336-1337November 2, 2000

Article

To the Editor:

Vichinsky et al. (June 22 issue)1 showed that among 538 patients with sickle cell disease who were followed for four years, 16 percent of 670 episodes of the acute chest syndrome were caused by a pulmonary infarction. A total of 29 percent of the episodes were associated with infections, some occurring together with infarctions, so that a cause of the acute chest syndrome was found in only 38 percent of episodes. However, infections were diagnosed mostly on the basis of seroconversion and the detection of microorganisms or chlamydia antibody in cultures of nasopharyngeal aspirates and sputum. The polymerase chain reaction (PCR) was only used to detect Chlamydia pneumoniae in nasopharyngeal samples. PCR techniques are more sensitive than serologic analysis, culturing, and antigen-detection assays for diagnosing some bacterial and most viral infections. So, it was not surprising that C. pneumoniae accounted for most of the infections diagnosed in the cohort (29 percent, or 71 of 249 infections). The incidence of mycoplasma infections and viral infections of the respiratory tract in particular was most likely underestimated because PCR was not used to detect these microorganisms in samples of respiratory secretions.

Pedro Avila, M.D.
University of California, San Francisco, San Francisco, CA 94143-0130

1 References

1. 1

   Vichinsky EP, Neumayr LD, Earles AN, et al. Causes and outcomes of the acute chest syndrome in sickle cell disease. N Engl J Med 2000;342:1855-1865
   Full Text | Web of Science | Medline

To the Editor:

Smoking and exposure to environmental tobacco smoke commonly cause or exacerbate acute diseases of the chest associated with infectious or noninfectious causes.1 It is plausible that disease related to exposure to tobacco smoke caused or contributed to the pathogenesis of the acute chest syndrome in the study by Vichinsky et al. Recent studies have demonstrated that both active smoking and passive smoking cause reversible endothelial dysfunction in humans2; vascular injury induced by tobacco smoke could promote intravascular sickling in situ and the lung injury seen in the acute chest syndrome. Furthermore, more than half the U.S. population is chronically exposed to environmental tobacco smoke,3 making it reasonable to assume that some patients in this study were at risk for respiratory disease related to environmental tobacco smoke; approximately one third of adults and teenagers who have sickle cell disease smoke cigarettes.

Stephen J. Jay, M.D.
Indiana University School of Medicine, Indianapolis, IN 46202-5114

3 References

1. 1

   Health effects of exposure to environmental tobacco smoke: final report. Sacramento: California Environmental Protection Agency, 1997.
   

2. 2

   Moreno H Jr, Chalon S, Urae A, et al. Endothelial dysfunction in human hand veins is rapidly reversible after smoking cessation. Am J Physiol 1998;275:H1040-H1045
   Web of Science | Medline

3. 3

   Pirkle JL, Flegal KM, Bernert JT, Brody DJ, Etzel RA, Maurer KR. Exposure of the US population to environmental tobacco smoke: the Third National Health and Nutrition Examination Survey, 1988 to 1991. JAMA 1996;275:1233-1240
   CrossRef | Web of Science | Medline

Author/Editor Response

The authors reply:

To the Editor: Dr. Avila raises an important point regarding the sensitivity of PCR in detecting infectious pathogens. Because our study included numerous centers, it was important to use the gold-standard diagnostic approach for each potential pathogen that could cause the acute chest syndrome in patients with sickle cell anemia. For this reason, we did not use PCR except to identify C. pneumoniae, since there is no agreed-on gold standard for the detection of this pathogen.1 The degree to which we may have underestimated the frequency of pathogens other than C. pneumoniae as a cause of the acute chest syndrome is unknown.

Although there may be a relation between smoking, exposure to environmental tobacco smoke, and the acute chest syndrome, our study was not designed to examine these potential factors in the pathogenesis of the acute chest syndrome.

Deborah Dean, M.D., M.P.H.
Lynne D. Neumayr, M.D.
Elliott P. Vichinsky, M.D.
Children's Hospital Oakland, Oakland, CA 94609

1 References

1. 1

   Verkooyen RP, Willemse D, Hiep-van Casteren SC, et al. Evaluation of PCR, culture, and serology for diagnosis of Chlamydia pneumoniae respiratory infections. J Clin Microbiol 1998;36:2301-2307
   Web of Science | Medline