Phosphate matters when investigating hypercalcemia: a mutation in SLC34A3 causing HHRH

[摘要] Hereditary hypophosphatemic rickets with hypercalciuria (HHRH) is a rare, autosomal recessive disorder caused by mutations in the SLC34A3A (p.G495R) missense mutation of the SLC34A3 gene. She was started on oral phosphate replacement which normalized her serum phosphate, serum calcium and urine calcium levels over the subsequent 5 years. HHRH is an autosomal recessive condition that causes decreased renal reabsorption of phosphate, leading to hyperphosphaturia, hypophosphatemia and PTH-independent hypercalcemia due to the physiologic increase in calcitriol which also promotes hypercalciuria. Classically, patients present in childhood with bone pain, vitamin D-independent rickets and growth delay. This case of a SLC34A3 mutation illustrates the importance of investigating chronic hypophosphatemia even in the presence of other more common electrolyte abnormalities. Learning points: Hypophosphatemia is an important diagnostic clue that should not be ignored, even in the face of more common electrolyte disorders. HHRH is a cause of PTH-independent hypophosphatemia that may also show hypercalcemia. HHRH is a cause of hypophosphatemic nephrocalcinosis that should not be treated with calcitriol, unlike other congenital phosphate wasting syndromes. Some congenital phosphate wasting disorders may not present until adolescence or early adulthood.

[学科分类] 血液学