Thus, children harboring a maternally inherited loss-of-function CaSR mutation typically have an FHH1 phenotype with asymptomatic hypercalcemia during infancy, whereas children who have not inherited a loss-of-function CaSR mutation from a mother with FHH1 may either be normocalcemic or develop transient neonatal hypocalcemia, which can be symptomatic and cause seizures. The gene discussed is CASR; the disease is hypercalcemia disease.