Role of biochemical laboratory on sclerosing bone disorders: Creatinkinase and osteopetrosis

Abstract

Introduction: Osteopetrosis (marble bone disease) is a rare type of sclerosing bone disorder, characterized by an altered functionality / morphology of the osteoclasts, which generates a defective bone resorption. The diagnosis is based mainly on radiographic findings. In most cases of osteopetrosis, the BB isoenzyme of creatine kinase (CK-BB), which is synthesized by osteoclasts, is increased. Thus, its serum determination may be useful for the study and identification of osteopetrosis.
Objectives: To alert against discordant results of Creatine kinase-MB (immunoinhibition), due to the interference produced by osteoclastic CK-BB in osteopetrosis, and to incorporate techniques of medium complexity, which allow recognizing CK-BB, in the study of this rare pathology.
Materials and Methods: Sera from four adult patients with diagnosis of osteopetrosis were used to determine: activity of: Creatine kinase and Aspartate-aminotrasferase (AST) (IFCC), Lactate-dehydrogenase (DGKC) and Creatine kinase-MB (immunoinhibition), in an autoanalyzer (COBAS 6000-Roche); and CK isoenzymes (electrophoresis).
Results: CK activities (three out of four patients) and AST (one out of four patients) were obtained in relation to the reference range; normal LDH (all patients); CK-MB (immunoinhibition) higher than total CK (three out of four patients). The presence of CK-BB (electrophoresis) was verified in the patients with discordant results of CK-MB. Conclusion: In patients with clinical and radiographic images that guide the diagnosis of osteopetrosis, the aberrant results obtained from CK-MB are due to the CK-BB contributed by the bones, which interferes as a methodological limitation. The presence of CK-BB in electrophoresis supports the diagnosis, excluding other sclerosing osseous diseases, providing