Pedigrees of the seven families
Filled symbols indicate spinal BMD Z score < −2.50; three/quarter-filled symbols indicate Z score between −2.50 and −2.00; half-filled symbols indicate Z score between −2.00 and −1.50; one/quarter-filled symbols indicate Z scores between −1.50 and −1.00; unfilled symbols indicate Z score >−1.00. Symbols with X indicate that the individual was not tested; symbols with + indicate anecdotal evidence of osteoporosis or radiographic evidence of osteopenia. Arrows indicate the proband in each family. Family 01 has one set of monozygotic twins.