[The bone in non-corticoid-treated sarcoidosis. A histomorphometric study].

The sarcoidosis granuloma secretes 1-25 dihydroxyvitamin D (1-25(OH)2 D) at the origin of the hypercalcemia found in about 20 p. cent of sarcoidoses. Its mechanism was considered exclusively of a digestive nature, but the activity of osteoclastic stimulation of 1-25(OH)2 D must consider an associated bony origin. Nine patients with bouts of non-steroid sarcoidosis were studied by osseous histomorphometric analysis. In a patient with hypercalcemia and radiographic manifestations, a high degree of bone remodelling is demonstrated, with stimulation of osteoclastic and osteoblastic activity. In eight patients with normocalcemia, two subgroups are individualized: two patients present intramedullary sarcoidosis granulomas with increased contact resorption; six patients present a normal marrow: the total areas of resorption remain increased. It is concluded that the activity of osteoclastic resorption is increased in sarcoidosis, which may explain partially the hypercalcemia. The absence of titration of 1-25(OH)2 D in our study does not permit to precise the role of this enzyme in the genesis of hyperosteoclastosis, although this seems quite plausible.