Idiopathic arterial calcification of infancy in newborn siblings with unusual light and electron microscopic manifestations.

We report two cases of idiopathic arterial calcification of infancy (IACI) occurring in newborn siblings. Unusual gross and light microscopic findings included calcification of multiple nonarterial tissues, renal infarction, and macroscopic aortic involvement. One case manifested an extensive acute panarteritis suggesting that IACI may be the result of an inflammatory or infectious process. Ultrastructural examination confirmed that the mineral deposits were hydroxyapatite and also indicated that they contained iron. Calcified tissue components included smooth-muscle cells, fibroblasts, and collagen fibers, as well as elastic fibers. No matrix vesicles or mitochondrial calcifications that may serve as nucleation sites for crystalline calcium phosphate were identified. Thus, the mechanism of calcification in IACI may be unique, and may relate to altered iron metabolism.