Zoledronic acid in osteoporosis secondary to mastocytosis

Osteoporosis is the prevalent manifestation of bone involvement in patients with systemic mastocytosis. Mastocytosis-related osteoporosis is characterized by both absolute and relative prevalence of osteoclastic activity, consistent with the positive results reported in small series of patients with antiresorptive drugs, such as bisphosphonates. The aim of this study is to investigate the efficacy of zoledronic acid in patients with mastocytosis-related osteoporosis.

Twenty-five patients with osteoporosis secondary to indolent systemic mastocytosis were given a single intravenous infusion of 5 mg zoledronic acid dissolved in 100 mL of 0.9% saline over 60 minutes.

After 1 year, the mean increase in bone mineral density was 6.0% ± 4.4% at the spine and 2.4% ± 3.2% at the total hip. Serum levels of bone turnover markers decreased versus baseline: bone alkaline phosphatase -34% and -35%, and C-terminal telopeptide -68% and -56% at 6 and 12 months, respectively. None of the patients reported new fractures during the year of follow-up. In all the first 20 treated patients, a transitory acute phase response was observed, but this was prevented in 4 of 5 subsequent patients in whom acetaminophen was given systematically during the 3 days post-infusion.

A single 5 mg zoledronic acid intravenous infusion in patients with osteoporosis secondary to indolent systemic mastocytosis is associated with significant increases in spine and hip bone mineral density and decreases of bone turnover markers over at least 1 year. Yearly zoledronic acid might represent a therapeutic option for indolent systemic mastocytosis-associated osteoporosis.