What are the causes of hypercalcemia in a child?

Causes of Hypercalcemia in Children

Hypercalcemia in children is most commonly PTH-independent (suppressed PTH) rather than PTH-dependent, with causes varying significantly by age—sepsis dominates in neonates while genetic syndromes, endocrine disorders, and malignancies become more prevalent in older children. 1, 2

Classification Framework

Pediatric hypercalcemia should be systematically categorized based on parathyroid hormone (PTH) levels into two major groups 1, 3:

PTH-Independent Hypercalcemia (Suppressed PTH)

This is more common in children than PTH-dependent causes 1:

Genetic/Congenital Causes:

• Idiopathic infantile hypercalcemia (IIH): Most common in the first 2 years of life, often resolves during childhood but lifelong calcium metabolism abnormalities may persist 4, 1, 3
• Williams-Beuren syndrome: Presents with increased calcium absorption from the gut (mechanism unknown), symptomatic hypercalcemia peaks in first 2 years, associated with dehydration, hypercalciuria, and nephrocalcinosis 4, 1, 3, 5
• Hypophosphatasia: Inborn error of metabolism 3, 5
• Other inborn errors of metabolism 1, 3

Acquired Causes:

• Hypervitaminosis D: Excessive vitamin D supplementation 1
• Granulomatous disorders: Including sarcoidosis 1
• Endocrinopathies: Congenital adrenal hyperplasia, Addison's disease, fat necrosis 1, 2
• Malignancy-related: Tumors producing PTH-related peptide or calcitriol 1
• Immobilization: Particularly in adolescents 5
• Milk-alkali syndrome 5

PTH-Dependent Hypercalcemia (Normal or Elevated PTH)

Genetic/Familial Causes:

• Familial hypocalciuric hypercalcemia (FHH): Autosomal dominant CASR mutations, can be homozygous with milder mutations 1, 2, 6
• Neonatal severe primary hyperparathyroidism (NSHPT): Severe form requiring urgent intervention 1, 3
• Familial isolated primary hyperparathyroidism 1
• Multiple endocrine neoplasia (MEN) syndromes: MEN1 and MEN2 with hyperparathyroidism developing at specific ages based on genotype—screening begins at 11 years for "high risk" and 16 years for "moderate risk" RET alleles 4, 1
• Jansen's metaphyseal chondrodysplasia: Activating PTH receptor mutations 3, 5

Acquired Causes:

• Primary hyperparathyroidism (PHPT): Parathyroid adenomas or hyperplasia 1, 6
• Tertiary hyperparathyroidism: Associated with chronic renal failure or hypophosphatemic rickets treatment 1
• Maternal hypocalcemia: Causes neonatal hyperparathyroidism 1, 3
• Extracorporeal membrane oxygenation (ECMO): In neonates 1

Age-Specific Considerations

Neonates and infants (0-2 years) have the highest frequency of severe hypercalcemia, accounting for 42% of sustained cases 2:

• Sepsis is the leading cause in neonates, representing 41% of all neonatal hypercalcemia cases 2
• Idiopathic infantile hypercalcemia and Williams syndrome present most commonly in this age group 4, 1, 3
• Maternal factors (hypocalcemia) and dietary causes must be evaluated 3

Older children and adolescents have different etiologies with lower overall frequency inversely related to age 2:

• Primary hyperparathyroidism becomes more common 1, 6
• Malignancy-related hypercalcemia increases 1
• Immobilization-related hypercalcemia can occur 5

Critical Diagnostic Pitfalls

Sustained vs. transient hypercalcemia: Only 63.3% of children with severe hypercalcemia (≥2.90 mmol/L) have sustained elevation (≥2 consecutive days); transient elevations may not require extensive workup 2

Williams syndrome surveillance: Serum calcium should be monitored every 4-6 months until 2 years of age, then every 2 years thereafter, as lifelong abnormalities in calcium and vitamin D metabolism persist even after symptomatic hypercalcemia resolves 4

MEN2 screening protocols: Hyperparathyroidism screening with serum calcium begins at age-specific intervals based on RET genotype risk stratification—"high risk" at 11 years, "moderate risk" at 16 years, with "highest risk" codon 918 variants not associated with PHPT 4

Frequency in clinical practice: Sustained severe hypercalcemia affects approximately 1 in 500 children in general hospital settings, making thorough investigation essential for all cases 2