familial hypocalciuric hypercalcemia

Epidemiology

• rare

Pathology

• reduced activity of Ca+2 sensing receptor (CASR)
• FHH is characterized by altered Ca+2 homeostasis

Genetics

• associated with a defect in Ca+2 sensing receptor (CASR) in parathyroid cells

Clinical manifestations

• generally asymptomatic

Laboratory

• serum calcium: mild to moderate hypercalcemia
• urine calcium:
  • low urinary Ca+2 excretion in distinction to hyperparathyroidism
  • 24 hour urine calcium < 200 mg/24 hours
  • urine calcium/creatinine ratio < 0.01
• serum creatinine & urine creatinine for calculation of calcium to creatinine clearance ratio
  • calcium [urine] (mg/dL) x creatinine [serum] (mg/dL)

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calcium [serum] (mg/dL) x creatinine [urine] (mg/dL)

• a ratio of < 0.01 suggests familial hypocalciuric hypercalcemia
• serum PTH is variable, may be high or inappropriately normal
• CASR gene mutation if diagnosis is clinically ambiguous

Differential diagnosis

• hyperparathyroidism
• idiopathic hypercalciuria
• absorptive hypercalciuria

Management

• benign condition
  • does not resolve with parathyroidectomy
  • no treatment indicated

More general terms

• genetic disease of the endocrine system
• hypercalcemia

More specific terms

• familial hypocalciuric hypercalcemia type I
• familial hypocalciuric hypercalcemia type II
• familial hypocalciuric hypercalcemia type III