Osteopetro-rickets: a new congenital bone disorder.

Two lethal mutations have been described in the rat: "osteopetrosis" (op) and "toothless" (tl). The op mutant can be cured by normal bone marrow infusion, while the tl mutant cannot. We report here additional data with regard to the tl mutant. The bone disease of the tl rat as in the op rat is associated with a precocious thymic atrophy, but bone lesions are quite different. In addition to classical osteopetrosis, the tl rat displays several features of rickets: broadening of the extremities of long bones, thickening of the epiphyseal plates, presence of osteoid areas. In addition, the persistence of embryonic characters, evidenced by high levels of alpha-fetoprotein, suggests that the developmental defect of bone is part of a more general process.

[Thymus and bones]. / Thymus et os.

Rat congenital osteopetrosis and cyclophosphamide (an immunosuppressive drug) induced osteocondensation are useful experimental models for the understanding of the relationships which seem to exist between thymus and bone. The high levels of seric alphafetoprotein found in the osteopetrotic tl rat raise the question of the persistance of embryonic characters in congenital osteopetrosis.