ESPE Abstracts (2019) 92 P2-30

A Rare case of Neonatal Hypocalciuric Hypercalcemia Complicated with Arrhythmia

Yuto Arai, Ryo Okumura, Soichiro Wada, Keiji Haseyama, Shuji Sai

Teine-Keijinkai Hospital, Sapporo, Japan

Background: Familial hypocalciuric hypercalcemia is a rare, lifelong, but benign hereditary disorder due to its mild, often asymptomatic phenotype. Here we present a rare case of neonatal hypocalciuric hypercalcemia complicated with arrhythmia.

Case: A healthy male infant weighing 2636g was delivered by spontaneous vaginal delivery at term. The pregnancy had progressed normally, but neonatal arrhythmia was found by physical examination after birth. Electrocardiography demonstrated isolated supraventricular premature contraction. The baby was well so that he was discharged on day 6 with further follow-up appointment at clinic. However, on day 10, he suffered from fever due to viral infection. Biochemistry investigations revealed markedly elevated serum levels of total calcium (Ca; 12.3 mg/dl; reference range: 8.8 – 10.1 mg/dl), and alkaline phosphatase (ALP 1863 U/L; reference range: 106 – 322 U/L). Serum concentration of phosphorus was normal (4.3 mg/dl: reference range: 2.7 – 4.6 mg/dl). Physical examination revealed no particular sign of hypercalcemia. Additional laboratory tests showed elevated intact PTH (88 mg/dl: reference range: 10 – 65 pg/mL and low renal calcium excretion (24-hour FECa < 1%). TSH and fT4 levels were slightly elevated (TSH 10.72 µIU/mL; reference range: 0.5 – 5.0 µIU/mL, fT4 2.02 ng/dL: reference range: 0.9 – 1.7 ng/dL) with no physical sign of hypothyroidism. Ultrasonography of the neck was performed which revealed no evidence of parathyroid adenoma. He was diagnosed with hypocalciuric hypercalcemia, although the family history of hypercalcemia was unremarkable. He was well on day 24 and the total calcium levels had been maintained at same levels without any treatment. Genetic sequencing of calcium sensing receptor gene mutation is under investigation.

Conclusion: Previous reports have shown that hypercalcemia in patients with primary hyperparathyroidism increased the occurrence of arrhythmia such as supraventricular premature contractions. Therefore, clinicians should consider electrolyte abnormalities including hypercalcemia in the differential diagnosis of neonatal arrhythmia.

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