PTHrP-related Hypercalcaemia in Infancy and Congenital Anomalies of the Kidney and Urinary Tract (CAKUT)

BACKGROUND: Severe hypercalcaemia is a rare but clinically significant condition in infancy and childhood. Parathyroid hormone-related peptide (PTHrP)-mediated hypercalcaemia resulting from a malignancy is rare and only a handful of case reports have outlined its incidence alongside a benign condition. OBJECTIVES: To describe the diagnostic workup and management of an infant with hypercalcaemia, renal dysplasia, and elevated PTHrP levels. DESIGN: Case report. SETTING: The Victoria Hospital campus of the London Health Sciences Centre in London, Ontario, Canada. PATIENTS: A child with congenital anomalies of the kidneys and urinary tract (CAKUT), stage 2 chronic kidney disease (CKD), and renal dysplasia who presented with severe hypercalcaemia. MEASUREMENTS: Weight, renal ultrasound, creatinine, cystatin C, eGFR, calcium, urea, bicarbonate, serum sodium, fractional sodium excretion, urine calcium to creatinine ratio, PTH, TSH, Free T4, AM cortisol, HMA, VMA, 25-vitamin D, 1,25 dihydroxy-vitamin D, calcitriol, vitamin A, ACE levels, skull and chest x-rays, alkaline phosphatase, CBC, tumour lysis profile, catecholamine breakdown, whole-body MRI, PTHrP. METHODS: Full diagnostic workup and patient management. Patient treated with intravenous hydration, furosemide, calcitonin and CalciLo. RESULTS: PTHrP was elevated and no evidence of a malignancy was found. Treatment consisting of a low-calcium CalciLo diet (in place of breast milk) adequately controlled the patient’s hypercalcaemia. Hypercalcaemia associated with CAKUT in infancy is not all that uncommon and was reported in 15/99 infants in another study, most of whom had a suppressed PTH similar to that of our patient. PTHrP was not measured in these cases and may have also been elevated. LIMITATIONS: The study is limited in that it is a description of a single patient case. Future measurement of PTHrP in similar patients is necessary to confirm our results. CONCLUSIONS: The possibility of elevated PTHrP levels must be considered in patients with known renal dysplasia who are differentially diagnosed with hypercalcaemia.