Pulmonary alveolar microlithiasis (PAM) is a rare idiopathic disease with unknown etiology and pathogenesis. The present work updates the world literature on PAM up to the end of 2001 by means of a full review, including minor reports in local languages (not English). Excluding secondary cases, a total of 424 cases have been reported worldwide, 269 of which were sporadic and showed a prevalence of the male sex and 155 of which were familial cases and prevalently affected the female sex. The highest number of cases has been reported in Europe, followed by Asia, especially Asia Minor, while the single nations with the greatest number of reported cases are Turkey, then Italy and the USA. The salient clinical features of PAM as described in the literature are analyzed: family history, clinical course, association with other diseases, presence of calcification in other organs. In the first cases, reported in the 60s and 70s, diagnosis was primarily made at autopsy, whereas nowadays diagnostic investigation is made above all by transbronchial biopsy and bronchoalveolar lavage. Radiological imaging is sufficient in cases where other family members are known to be affected, diagnosed by means of invasive techniques. There is no known treatment to date, while lung transplantation is performed in the severest cases. A better knowledge of the epidemiological characteristics of this rare disease could help to diagnose a larger number of cases and to gain insight into its etiology and pathogenesis, which are still unknown.

Pulmonary alveolar microlithiasis (PAM) (MIM 265100) is a rare, autosomal recessive pneumopathy characterized by intra-alveolar formation and accumulation of tiny, roundish corpuscles called "microliths". The name "alveolar microlithiasis" was first used by Puhr in 1933; since then, several reports have appeared, and over 300 individuals with this condition have been reported. We have reviewed the PAM cases in the literature in light of personal experience, focusing on medical implications, disease diagnosis and progression over time, familial predisposition, and geographical and sex distribution. This study confirms autosomal recessive inheritance and does not support the role of other, non-genetic, factors in the pathogenesis of PAM.

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