Anatomy and Histology of Fatal Cases

The evidence that is available regarding the morbid anatomy of idiopathic hypercalcemia of infancy is naturally derived from severer cases which have proved fatal (D3, L6, Rl, S2). In these, pathological changes are found predominantly in the skeleton, kidneys, and cardiovascular system, but other systems may be involved to a lesser degree. 

These may be normal or considerably reduced in size. The surface is smooth. On section the cortex may be seen to be narrowed. The cut surface may show minute calcium deposits in the medulla, especially the outer medulla, and in the cortex. Microscopically the lesions are found 

The renal lesions which have been described in idiopathic hypercalcemia are not specific. Similar changes have been observed in hyperchloremic renal acidosis of infancy (B7, D7), in various other diseases of infancy and in hypervitaminosis D. It is interesting to note that a recent re-examination of the histological sections of Thatcher s cases of a quarter of a century ago showed that the changes there were essentially the same as those occurring in idiopathic hypercalcemia of infancy (Rl). 

The heart may be enlarged with left ventricular hypertrophy, particularly in cases which have exhibited hypertension during life. Metastatic calcification of the valves and of the myocardium may be present, explaining no doubt the cardiac murmurs which may have been detected clinically in such cases. Occasionally, medullary proliferation of large arteries and, in the smaller arteries, fragmentation of the intimal elastic lamina has been reported, in one case with impregnation with calcium salts. Local calcification of the media of the middle cerebral artery has been described. 

The bones may appear normal but may show increased sclerotic change coinciding with the areas of increased radiological density, i.e., 

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