[Pulmonary alveolar microlithiasis. One case (in a child) with ultrastructural analysis and micro-probe analysis (author's transl)].

Authors report on case of pulmonary alveolar microlithiasis with typical chest X-ray, in a six years old boy (without other case of microlithiasis in his family). Pulmonar biopsy shows numerous heavily mineralised microliths in alveolar lumens. Elementary chemical analysis of the microliths (by micro-probe or "ionic" analysis) detects calcium, phosphorus, potassium, sodium, magnesium and carbon, without any exogenous metal. Study (of decalcified tissue) with electronic microscope shows the substrate of mineralisation to ber made of amorphous, non fibrillar, material. In the center of some microliths, membranous structures (possible of cellular origin) were seen. By histochemical study this substrate seems to be a mucoproteic complex with non-sulfated acid polysaccharide component. Histogenesis of such microliths is therefore discussed.