Congenital bowing of the long bones. A review and phenotype analysis of 13 undiagnosed cases.

Phenotype analysis of 13 patients with congenital bowing of long bones and otherwise undiagnosable conditions allowed sorting into three major groups. Patients in group 1 had normal bone texture; bowing was confined to the femora, the long bones were relatively thin, there were no epiphyseal or metaphyseal abnormalities, and associated malformations or CNS abnormalities were common. Patients in group 2 had osteopenia; bowing was more generalized, the long bones were relatively thick, there were metaphyseal ossification abnormalities. Two brothers belonged to a third group with normal bone texture, relatively thick bones, bowing of the upper and lower limbs, and metaphyseal abnormalities. The subdivision of patients with congenital bowing of the long bones in these groups may be biologically significant. The occurrence of malformations only in group 1 is remarkable. Osteopenia, as found in patients of group 2, may be an important pathogenetic factor not present in patients of groups 1 and 3. Known causes of congenital bowing of long bones are tabulated.