In mammalian
osteopetrosis the different mutations exemplify reduced
bone resorption leading to net accumulation of bone. Recently, high blood levels of
creatine kinase-BB have been reported in some human forms, suggesting it as a marker of
osteopetrosis. In the current study serum
creatine kinase-BB was evaluated in relation to known osteoclastic pathophysiology in two human types of autosomal dominant
osteopetrosis at baseline and after stimulation with
triiodothyronine and in four different rodent mutations.
Creatine kinase-BB was increased markedly in Type 2 autosomal dominant
osteopetrosis and in the incisors absent rat, both characterized by large numbers of giant osteoclasts, and did not change significantly after stimulation. Although
creatine kinase-BB was unchanged in Type 1 autosomal dominant
osteopetrosis at baseline and after stimulation, the rodent counterparts characterized by small osteoclasts, microphthalmic and osteopetrotic mice and toothless rats, had significantly decreased levels. Similar differences were observed in both types of autosomal dominant
osteopetrosis compared with controls concerning
tartrate resistant acid phosphatase.
Creatine kinase-BB in mammalian
osteopetrosis is related to osteoclastic number and size, where it probably reflects the differentiation and maturation of inactive bone resorbing cells. The
isoenzyme does not seem to be a valuable screening marker for
osteopetrosis.