Pulmonary alveolar microlithiasis

Pulmonary Alveolar Microlithiasis (PAM) is a rare disease characterized by calcium salt deposits within the alveoli. In the literature, about 700 cases have been published up to April 2012. The disease develops slowly and is characterized by a progressive lung involvement, starting from the lower lobes with extension to the middle and upper lung zones. The chest radiograph gives a picture sandstorm-like which is often the first sign in the absence of clinical symptoms. The characteristic high resolution computed tomography (HRCT) is pathognomonic of the disease and the diagnosis is made, especially if the microliths are found in the BAL. Rarely, a biopsy is necessary for diagnosis. Recently in these subjects was highlighted a mutation of SLC34A2 gene, which regulates the cotransport of sodium and phosphate within alveolar type II cells. It is thought that the gene mutation compromises the normal production of the protein which is involved in the clearance of the phosphorus ion from the alveolar spaces and this alteration causes the progressive accumulation of microliths. In this chapter, the incidence of the disease in the literature, the current pathogenetic hypotheses, the clinical features, the diagnostic criteria, and finally, the current therapeutic attempts are reviewed. characterized by the progressive accumulation of calcifi c elements, the microliths or calcospherites, into the alveolar spaces.