Diagnosing pulmonary alveolar proteinosis: Is there any role of radiology?

Abstract

Dear Editor, We read with interest the article titled “Primary alveolar proteinosis – A report of two cases” written by Bhattacharyya et al1 and published in MJAFI 2013;69:90-93. Having gone through the article, we would like to emphasize certain facts which might be relevant to all of us. The authors have presented four axial images of CT scan of chest, one photomicrograph of histopathology of open lung biopsy, one photograph depicting lung lavage fluid samples in serial order from case 1 and one axial image of CT scan of chest from case 2 in support of the case reports. The key words mentioned in the article are 1) Pulmonary alveolar proteinosis, 2) Whole lung lavage and 3) Granulocyte–macrophage colony stimulating factor. It is surprising that HRCT scan chest is not listed in the key words. As mentioned in the case history, both the cases were treated empirically with ATT despite sputum being negative for AFB and chest radiograph depicting bilateral extensive alveolar opacities. It would not be incorrect to assume at this point that the working diagnosis before the CT scan studies was pulmonary tuberculosis. Having gone through the cases mentioned in the article, it is quite evident that CT scan chest had played a decisive role in directing further investigations for confirming the diagnosis. The authors portray the HRCT findings as ‘crazy paving pattern’ in both the cases without any mention about the radiological diagnosis. It is on record that pulmonary alveolar proteinosis (PAP) was given as the first radiological diagnosis based on CT scan findings in both the cases despite the clinical diagnosis being pulmonary tuberculosis. It would be pertinent to mention here that radiological diagnosis of PAP was not made on the basis of ‘crazy paving pattern’ alone. Due consideration was given to the clinical setting in each case before suggesting the possibility of PAP. In fact, in case 2, bronchoalveolar lavage (BAL) was suggested after the CT scan study. It may also be relevant here to mention that, although ‘crazy paving pattern’ on HRCT chest in an appropriate setting is highly characteristic of PAP, there are a host of other conditions e.g. infectious (pneumocystis carinii pneumonia), neoplastic (mucinous bronchoalveolar carcinoma), idiopathic (sarcoidosis, non-specific interstitial pneumonia, organizing pneumonia), inhalational (lipoid pneumonia), misc (adult respiratory distress syndrome, pulmonary hemorrhage) and many more which can cause similar appearance on HRCT chest. The authors mention that both the cases were successfully managed with whole lung lavage. It is also mentioned that there was marked improvement in the condition of both the patients after one week of BAL. There is however, no follow up available for either of the patients. It is well known that patients of PAP may require repeat BAL after a certain interval of time which may vary from patient to patient. Some of the patients do not show any remission and rather worsen in severity. Hence, is it appropriate to comment on the success of BAL just on the basis of one week of observation? For the benefit of readers of the MJAFI, we illustrate serial CT scan findings of case 2 who was followed up with CT scan once after nearly six months and then exactly after 2 years (Fig. 1). The follow up images available with us, depict only partial resolution of lesions even after two years. Fig. 1 Serial axial CT scan sections (lung window) at immediate infra-carinal (a–c) and mid cardiac level (d–f) depicting partial clearance of lesions after nearly six months (b, e) and two years (c, f). Overall, we find that the role of radiology has been understated by the authors in the diagnosis and management of both these cases. This is likely to give an erroneous message to the readers of the esteemed journal of the AFMS.