Nanobacteria and psammoma bodies: ultrastructural observations in a case of pathological placental calcification.

Nanobacteria are controversial infectious agents with nanometric size, the capacity to nucleate hydroxyapatite and grow in culture, and present in human diseases associated with calcification and psammoma bodies. The authors report a case of pathological placental calcifications associated with nanobacteria. Electron microscopy and electron energy loss spectroscopy imaging were used to recognize 160-nm-sized calcium-free bodies mainly presenting as extracellular fibrillary tangles and 500-nm-sized calcified bodies; they encrusted the syncito-trophoblast basal membrane and aggregated into miniaturized psammoma bodies. Nanobacteria may be composed of a prionoid protein with self-assembling and self-propagating abilities whose growth is associated with the formation of psammoma bodies.