Lung calcification in long-term dialysed patients: a light and electronmicroscopic study

Lung calcification was detected in four out of 29 long-term dialysed patients on whom postmortem examinations were performed between 1967 and 1980. On light microscopy, calcification showed either a finely granular and linear localization along the alveolar septa, or a coarse and widespread parenchymal distribution. Histochemical studies revealed evidence of calcium, magnesium and phosphate ions in the deposits. Ultrastructural examination of the less severely involved alveolar septa showed selective deposition of calcium salts within an increased amount of elastin. The deposits consisted of electron dense roundish granules with a concentric laminar structure. They appeared either single or conglomerated in polycyclic formations, supposedly representing the progressive steps of the mineralization process, at first localized within elastin and progressively spreading outside it. The high magnesium content of the deposits suggests that the serum concentration of this ion may play an important role in visceral calcification of long-term dialysed patients.