PTH and hypercalcemia disease: Hypercalcemia is not a feature of the OPTs unless following restoration of OC action by marrow cell transplantation.(38, 39) In our initial patient harboring SLC29A3 mutations,(4, 5) serum ionized calcium was high‐normal at approximately 1 year old, but decreased after excessive dietary calcium was corrected.(4) In DSS, low serum PTH levels can occur,(9, 10) suggesting mineral homeostasis is impacted.