Background: Pulmonary alveolar microlithiasis (PAM) is a rare, chronic lung disease with unknown etiology and with a nonuniform clinical course. Nonuniformity of clinical course might be related to the degree of pulmonary parenchymal alterations, which can be revealed with high resolution computed tomography (HRCT). However, HRCT findings of PAM were not fully described in the current literature.
Aim: The aim of this study was to interpret and to contribute to describe HRCT findings of PAM and to investigate a correlation between profusion of micro nodules (MN) and pulmonary parenchymal alterations in patients with PAM.
Material and methods: Ten male patients with PAM (mean age: 22+/-3.2) were included into the study. HRCT images were assessed for patterns, distribution, and profusion of pulmonary abnormalities. Dividing the lungs into three zones, profusion of abnormalities was assessed. A profusion score (1-4) was given and the scores of each zone were then summed to obtain a global profusion score for HRCT ranging from 0 to 12. Also a parenchymal alteration score (PAS) was defined with respect to profusion of abnormalities. Chest X-rays were also scored.
Results: All of ten patients with PAM had findings of interstitial lung disease in varying degrees on their HRCTs. HRCT findings of patients with PAM were as following: MN, parenchymal bands (PB), ground glass opacity (GGO) and, sub pleural interstitial thickening (SPIT) in 10 patients; interlobular septal thickening (ILST), in 9 patients; paraseptal emphysema (PSA) in 8 patients; centrilobular emphysema (CLA) in 7 patients; bronchiectasis (BE), confluent micro nodules (CMN) in 6 patients; peri bronchovascular interstitial thickening (PBIT) in 5 patients; panacinar emphysema (PANAA) in 3 patients; pleural calcification (PC) in 2 patients. A significant correlation between MN scores and PAS (r=0.68, p=0.031, MN scores and GGO scores (r=0.69, p=0.027) and, MN scores and CLA scores (r=0.67, p=0.034) was detected. We also found significant correlations between HRCT scores and results of pulmonary function tests (PFTs), HRCT scores and chest X-ray score (CXRS) and, CXRS and results of PFTs.
Conclusion: We conclude that patients with PAM may have all findings of interstitial lung disease in varying degrees as well as MNs on their HRCTs. More importantly, this study suggests a proportional relationship between profusion of MNs and parenchymal alterations in patients with PAM. This study also suggests that the degree of parenchymal alterations closely related with the degree of pulmonary function loss in patients with PAM.