E-Poster Presentation ESA-SRB-ANZBMS 2021

We present a case of a 71-year-old with hypercalcemia and disseminated granulomatous tuberculosis, with response to cinacalcet despite normal PTH, PTHrP, and 1,25(OH)₂

She was diagnosed with disseminated tuberculosis disease whilst being worked up for unintentional weight loss. She was noted to be hypercalcaemic with a peak corrected calcium of 3.70 mmol/L. Myeloma screens, thyroid function, serum ACE were normal. 1,25(OH)₂D was 124 nmol/L (60-200) and 25(OH)₂D was 99 nmol/L. PTHrP was undetectable at <1.0 pmol/ (<1.05), and PTH was low at 0.6 pmol/L (1.6-6.9).

The Time course of serum calcium and management is shown in the figure. Cinacalcet 30 mg TDS was commenced with a decrease in serum corrected calcium from 3.7 mmol/L to 2.8 mmol/L within 96 hours.

Discussion

This case demonstrates an unusual picture of severe hypercalcaemia in granulomatous disease resistant to other treatment modalities but responsive to cinacalcet despite suppressed PTH and PTHrP.

Cinacalcet is a type II Calcimimetic that modulates the activity of the CaSR to increase its sensitivity to extracellular calcium and inhibit PTH release. ⁱⁱ  Possible mechanisms of cinacalcet, in this case, include via PTH or PTHrP not detectable in our assay, or CaSR-mediated reduction in renal calcium absorption. .[i] [ii]

To the best of our knowledge, this is the first report of hypercalcaemia in granulomatous disease response to calcimimetics.