Paediatrics: Hypercalcaemia

Hypercalcaemia

There are a number of different causes of high plasma calcium levels:

·  William’s syndrome.

·  Idiopathic infantile hypercalcaemia.

·  Hyperparathyroidism.

·  Hypercalcaemia of malignancy.

·  Vitamin D intoxication.

·  Familial hypocalciuric hypercalcaemia.

Other uncommon causes include: sarcoidois and other granulomatous disease; chronic immobilization; renal failure; hyperthyroidism; Addison’s disease; iatrogenic, e.g. thiazide diuretics.

Clinical features

Symptoms and signs of hypercalcaemia are non-specific.

·  GI: anorexia; nausea and vomiting; failure to thrive; constipation; abdominal pain.

·  Renal: polyuria and polydipsia.

·  CNS: apathy; drowsiness; depression.

Investigations

Laboratory

·  Plasma calcium (total and corrected for albumin).

·  Serum PTH.

·  Vitamin D metabolites.

·  U&E/LFTs.

·  TFT.

·  Urinary calcium excretion (UCa:UCr ratio; 24hr UCa).

Radiological 

Renal US scan (screen for nephrocalcinosis).

Treatment

Chronic treatment 

Directed at the underlying cause.

Hyperparathyroidism

Uncommon in children, excessive production of PTH may result from a primary defect of the parathyroid glands or may be secondary and com-pensatory to either hypocalcaemia or hyperphosphataemic states.

·p hyperparathyroidism:

·  parathyroid adenoma;

·  parathyroid hyperplasia: MEN type 1; MEN type 2; neonatal severe form.

·s hyperparathyroidism:

·  hypocalcaemic states—rickets;

·  hyperphosphatemia—chronic renal failure.

·Transient neonatal hyperparathyroidism: maternal hypoparathyroidism.

Primary hyperparathyroidism

Rare in children. In the neonatal period it usually associated with general-ized parathyroid hyperplasia. In older children it is usually due to a para-thyroid adenoma and most often associated with MEN type 1.

Transient neonatal hyperparathyroidism

Observed in neonates born to mother with previously undetected and/ or untreated hypoparathyroidism or pseudohypoparathyroidism. Chronic intrauterine hypocalcaemia results in hyperplasia of the foetal parathyroid glands.

Neonatal severe hyperparathyroidism 

See Familial hypocalciuric hyper-calcaemia.

Hypercalcaemia of malignancy

Rarely, in children with endocrine tumours (e.g. phaeochromocytoma) or other tumours (e.g. lymphoma), production of humoral factors such as PTH-related peptide (PTHrP) results in hypercalcaemia.

Treatment requires resection and removal of the tumour to reverse the hypercalcaemic state. Interim control can be achieved with a single IV infusion of a bisphosphonate agent, e.g. pamidronate. The latter enhances calcium bone resorption.

Familial hypocalciuric hypercalcaemia

Autosomal dominant disorder caused by a mutation of the calcium-sensing receptor (CaSR) gene. This is a benign, mostly asymptomatic disorder, which is often an incidental finding during routine biochemistry analysis. Plasma calcium levels are raised (but usually <3mmol/L), and urinary calci-um excretion is low. PTH levels are inappropriately normal for the degree of hypercalcaemia.