Two Cases of Symptomatic Familial Hypocalciuric Hypercalcemia: Treatment Response to Calcimimetic Therapy

Familial hypocalciuric hypercalcemia (FHH) is marked by mild to moderate hypercalcemia, normal-elevated serum PTH levels, and relative hypocalciuria. Cinacalcet, a calcimimetic therapy, has been reported to reduce symptom burden and serum calcium levels in FHH. We report 2 adult males with chronic hypercalcemia, with initial concerns for primary hyperparathyroidism. Urine calcium screening and genetic testing confirmed FHH in both patients. Shortened QTc normalized while on cinacalcet in the first patient and reductions in serum calcium and PTH levels without symptomatic hypercalcemia were noted in the second patient. Calcimimetic therapy can potentially be offered to FHH patients, particularly those with hypercalcemia symptoms, serum calcium levels >1 mg/dL (0.25 mmol/L) above normal or at risk of cardiac arrhythmias. Cinacalcet treatment was overall well tolerated and significantly reduced serum calcium and PTH levels in 2 adult FHH patients over time. Calcimimetic therapy has shown promise in managing persistent hypercalcemia and potential adverse events in FHH patients. Potential barriers include indefinite treatment, cost, and possible adverse effects.