Pulmonary alveolar microlithiasis: imaging characteristics of planar and SPECT/CT bone scan versus 18F-FDG and 18F-sodium fluoride PET/CT scanning.

Pulmonary alveolar microlithiasis (PAM) is a very rare disease in which multiple microscopic calcium phosphate microliths are deposited within the alveoli of both lungs. A lung biopsy is considered to be definitive for final diagnosis; however, non-invasive imaging modalities such as chest X-ray, HRCT scan and (99m)Tc-MDP bone scan suggest the diagnosis in the vast majority of patients. Although (18)F-FDG PET/CT has been tried to characterize the disease, (18)F-sodium fluoride PET/CT as a 'proof-of-principle' was tried for the first time in a known case of PAM in order to characterize the lung lesions. Interestingly, we noted that (18)F-sodium fluoride PET/CT is a superior modality in characterization and assessment of the extent of disease in PAM compared to all other non-invasive imaging modalities. Thus, we recommend that (18)F-sodium fluoride PET/CT should be the investigation of choice in PAM.