Familial hypocalciuric hypercalcemia is characterized by which inheritance pattern?

• A. Autosomal recessive
• B. Autosomal dominant
• C. X-linked
• D. Mitochondrial

Answer: (B)

Autosomal dominant. This condition stems from inactivating mutations in the calcium-sensing receptor (CaSR), which is expressed in the parathyroid and kidney. When one copy of the receptor is defective, the body’s calcium-sensing set-point shifts upward, so calcium levels rise and urinary calcium excretion remains relatively low. Because a single mutated allele can produce this phenotype, the trait commonly runs in families with vertical transmission across generations. In contrast, autosomal recessive would require two mutant alleles, X-linked would show a different male/female pattern, and mitochondrial inheritance follows maternal lines.