Letter Regarding "Granulomatous Inflammation and Hypercalcemia in Patients With Severe Systemic Oxalosis".

To the Editor:

Perrin et al. have reported a case series of 5 patients suffering from primary hyperoxaluria and systemic oxalosis who presented with inflammatory lesions on fluorodeoxyglucose-positron emission tomography/computed tomography and mild hypercalcemia. Biopsy results of the bone lesions revealed calcium oxalate deposits and granuloma with macrophages expressing RANKL. On the basis of these results, denosumab was administered to lower calcemia, with only mild effect.

We recently reported a similar presentation of primary hyperoxaluria with severe hypercalcemia and high 1,25(OH)2 vitamin D level. In our case, the hypercalcemia was probably triggered by excess of vitamin C administration, leading to increased oxalate deposits and activation of a tissular granulomatous response. As in the series by Perrin et al., a bone biopsy result revealed calcium oxalate deposits with numerous inflammatory granulomas. On the basis of previous publications reporting treatment of sarcoidosis-induced hypercalcemia with ketoconazole, we tried it unsuccessfully (Figure 1). Nevertheless, low-dose corticoid treatment (prednisone 15 mg/d) rapidly normalized serum calcium and 1-25(OH)2 vitamin D level. A maintenance therapy with 7.5 mg prednisone per day was enough to prevent recurrence of hypercalcemia.

Figure 1

Evolution of phosphocalcic parameters. M, month.

As denosumab is known to cause severe hypocalcemia in patients with chronic kidney disease and as discontinuation of treatment is associated with high risk of vertebral fractures, we propose that low-dose corticoid therapy should be considered first for hypercalcemia-associated oxalosis in patients with primary hyperoxaluria., Finally, vitamin C supplementation needs to be provided with caution and only under close monitoring in patients with primary hyperoxaluria with low estimated glomerular filtration rate.