Serum brain-type creatine kinase increases in children with osteogenesis imperfecta during neridronate treatment

BACKGROUND: Creatine kinase (Ck) catalyzes the reversible transfer of high-energy phosphate groups between adenosine triphosphate and phosphocreatine. The brain isoform (Ckbb) is greatly induced in mature osteoclasts, playing an important role in bone-resorbing function during osteoclastogenesis. High Ckbb serum level has been found in patients with osteopetrosis and in patients with bisphosphonate (BP)-induced osteopetrosis. BPs are considered the treatment of choice for children with osteogenesis imperfecta (OI), acting as potent inhibitors of bone resorption by suppressing the activity of osteoclasts. METHODS: We determined total serum Ck and isoform activity in 18 prepubertal children with type I OI, before and during treatment with the BP neridronate infusions. RESULTS: Basal serum Ckbb levels were slightly elevated with respect to controls (mean +/- SD = 3.0 +/- 2.7 vs. 2.0 +/- 2.2) and progressively increased after neridronate treatment (t(0) vs. t(4): mean +/- SD = 3.0 +/- 2.7 to 10.8 +/- 8.1), with significant increment after first, second, and fourth infusions (P < 0.01). An inverse correlation was found between serum Ckbb and serum CTx at basal level. CONCLUSION: Our results support previous observations that increased serum Ckbb reflects failure of osteoclasts or, at least, suppression of osteoclasts. Upon considering that BPs are long acting, this information could be useful to prevent the risk of overtreatment after long-term BP exposure in pediatric patients with OI.