Genetic variants that result in missense mutations in GCM2, which is a nuclear transcription factor required for parathyroid gland organogenesis named for its homology to the “glial cells missing” (gcm) gene in Drosophila, were recently discovered in the germline DNA of eight different families with FIHP (21). The gene discussed is GCM2; the disease is familial isolated hyperparathyroidism.