Bone histomorphometry in a long-term hemodialysis patient with hypoparathyroidism and sarcoidosis

A bone biopsy specimen in a long-term hemodialysis patient with sarcoidosis coexisting with severe hypoparathyroidism has demonstrated that a persistent near physiological level of 1,25-dihydroxyvitamin D₃ contributes to the preservation of bone remodeling and has the potential to retard the development of vascular calcification and atherosclerosis. Sarcoidosis-related hypercalcemia and hypoparathyroidism, which is characterized by 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) overproduction, is rarely seen in hemodialysis patients. Herein, we describe a 60-year-old Japanese woman on hemodialysis for 35 years who presented with malaise and hypercalcemia. Severe hypoparathyroidism without parathyroidectomy and a preserved 1,25(OH)₂D₃ level were detected. Computed tomography showed bilateral axillary lymphadenopathy and minimal aortic and soft tissue calcification. The axillary node biopsy led to a definite diagnosis of sarcoidosis. A bone biopsy specimen obtained from the right iliac crest showed remodeling of normal lamellar bone with scalloped cement lines and clear double labeling by tetracycline on fluorescence microscopy. Histomorphometric analysis revealed that the bone formation rate was preserved (30.0 %/year), together with a decrease of osteoid volume (5.75 %) and fibrous volume (0 %), indicating that the patient did not have adynamic bone disease and only showed mild disease. This is the first documented case of sarcoidosis-related hypercalcemia associated with severe hypoparathyroidism in a long-term hemodialysis patient who underwent bone histomorphometry. Our findings suggest that, in hemodialysis patients with sarcoidosis coexisting with severe hypoparathyroidism, a persistent near physiological level of 1,25(OH)₂D₃ contributes to the preservation of bone remodeling and has the potential to retard the development of vascular calcification and atherosclerosis.