Chest
Volume 136, Issue 5, November 2009, Pages 1348-1355
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Original Research
Pulmonary Alveolar Proteinosis
Comparative Study of High-Resolution CT Findings Between Autoimmune and Secondary Pulmonary Alveolar Proteinosis

https://doi.org/10.1378/chest.09-0097Get rights and content

Background

Acquired pulmonary alveolar proteinosis (PAP) has been reclassified into autoimmune or secondary PAP according to the occurrence of serum granulocyte macrophage colony-stimulating factor autoantibody. Most patients undergo high-resolution CT (HRCT) scanning in order for physicians to make a differential diagnosis of diffuse lung diseases, but no information is available to distinguish the HRCT scan features of secondary PAP from those of autoimmune PAP. The objective of this study was to characterize the HRCT scan features of autoimmune and secondary PAP.

Methods

HRCT scans of 42 patients (21 patients each in the autoimmune PAP and secondary PAP groups) were centrally collected and evaluated in a blinded manner.

Results

Ground-glass opacities (GGO) were a major finding in both the autoimmune PAP and secondary PAP groups. In the secondary PAP group, GGOs typically showed a diffuse pattern (62%), whereas GGOs showed a patchy geographic pattern in the autoimmune PAP group (71%; p < 0.005). The so-called “crazy-paving” appearance and subpleural sparing were frequently seen in the autoimmune PAP group (both 71%), whereas they were less frequently seen in the secondary PAP group (14% and 33%, respectively). The involved area of GGO was even in craniocaudal distribution for the secondary PAP group, whereas it was predominant in the lower lung field compared with the upper lung field in the autoimmune PAP group (p < 0.05).

Conclusions

Typical HRCT scan findings for autoimmune PAP patients were GGO with a patchy geographic pattern, subpleural sparing, crazy-paving appearance, and predominance in the lower lung field. These findings were rather infrequent for secondary PAP patients.

Section snippets

Patients

Twenty-one patients with autoimmune PAP and 21 patients with secondary PAP were enrolled in this study in Japan between May 2001 and March 2008. We obtained agreement from all treating physicians for each identified case according to the Guidelines for Epidemiologic Studies by The Ministry of Health, Labor, and Welfare, and clinical information was handled in a deidentified manner.15 This retrospective study was approved by the Ethical Board of Kyorin University (Mitaka, Tokyo, Japan). As a

Results

A total of 42 patients were enrolled in this study. Characteristics and demographics are shown in Table 1. Age and gender were similar between both the autoimmune and secondary PAP groups. Although P(A-a)O2 was similar between the groups at the registration, dyspnea on exertion was less frequent in the secondary PAP group than in the autoimmune PAP group. On the other hand, fever was observed in six patients with secondary PAP, but none with autoimmune PAP. Serum markers showed no difference

Discussion

The purpose of this study was to clarify the characteristics of HRCT scan features of PAP on the basis of the occurrence of serum GM-CSF autoantibody. As most cases of acquired PAP are classified into autoimmune or secondary PAP according to the presence or absence of serum GM-CSF autoantibody, it is rational to reevaluate and distinguish the HRCT scan characteristics between each type of PAP. We evaluated HRCT scan findings for 21 patients each with secondary PAP and autoimmune PAP to

Acknowledgments

Author contributions: Drs. Ishii, Trapnell, Akira, Goto, and Nakata completed the data analyses and prepared the manuscript. Drs. Tazawa, Inoue, Kogure, Tomii, Takada, Hojo, and Ichiwata provided the patient samples, HRCT scans, and clinical information. Dr. Nakata had access to and takes responsibility for the integrity of the data and the accuracy of the data analysis.

Financial/nonfinancial disclosures: The authors have reported to the ACCP that no significant conflicts of interest exist with

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Funding/Support: This study was supported in part by grant Category B18406031 from Japan Society for the Promotion of Science; in part by grant H14-trans-014 from the Ministry of Health, Labor, and Welfare of Japan; and by grants from the Ministry of Education, Culture, Sports, Science, and Technology of Japan.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/site/misc/reprints.xhtml).

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A complete list of participating hospitals is located in the Appendix.

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