An 8-month-old infant with hypercalcemia and hyperphosphatemia—Answers

Excerpt

Hyperphosphatemia in children is caused by several different etiologies including kidney failure, vitamin D toxicity, tumor lysis syndrome, tissue necrosis, and endocrine disorders including hypoparathyroidism, pseudohypoparathyroidism, secondary hyperparathyroidism, diabetic ketoacidosis (DKA), and severe hyperglycemia [1]. The principal causes of hyperphosphatemia are low levels of parathyroid hormone (PTH), decreased renal response to PTH, transcellular shifts from intracellular to extracellular spaces (DKA, lactic acidosis, severe hyperglycemia, crush injury, rhabdomyolysis or tumor lysis syndrome), increased intake of phosphate (rectal enema or intravenous replacement), and increased absorption (vitamin D toxicity) [2]. In our case, the levels of PTH, blood glucose, and arterial blood gas analysis were normal. There was also no previous history of malignancy, injury, or excessive use of vitamin D. Since there was no evidence for other differentials, and our patient also had a moderately decreased eGFR due to posterior urethral valve (PUV) and renal dysplasia, the high phosphate level was considered to be related with chronic kidney disease (CKD). In addition to this high phosphate level, a high calcium level was also observed in these patients because of higher levels of the parathyroid hormone [3]. However, since PTH level was normal in our patient, hypercalcemia was not considered to be related with kidney disease. The blood calcium levels of the parents were investigated and found to be normal. In addition, since urinary calcium excretion was also normal, genetic analysis for CaSR mutation was planned. Given a history of craniosynostosis and right posterior plagiocephaly along with hypercalcemia and hyperphosphatemia, the levels of serum PTH, 25(OH) vitamin D, 1.25(OH) vitamin D, and thyroid hormones were tested in order to rule out hyperparathyroidism, vitamin D intoxication, and thyroid diseases, the results of which fell within normal ranges. However, the serum alkaline phosphatase (ALP) level was found to be low (36 IU/L (N 83-469)), indicating the possibility of various disorders including hypophosphatasia, osteogenesis imperfecta, malignancies, surgeries, traumas, starvation, and nutrient deficiencies [4]. …