Interferon alpha and pamidronate in osteoporosis with fracture secondary to mastocytosis

The mechanism of osteoporosis with fracture secondary to mastocytosis is little known, and its treatment is poorly codified.

Ten patients with a mean age of 52.5 years with systemic mastocytosis and osteoporotic fractures were treated with interferon alpha 1.5 million U 3 times per week, combined with monthly pamidronate infusions (1 mg/kg) for 2 years, followed by pamidronate infusions every 3 months.

Before treatment, the mean number of vertebral fractures was 3.5, spinal T-score was -3±1, hip T-score was -1.9±0.7, serum C-terminal telopeptide was 357±258 pg/mL (N=80-800), bone alkaline phosphatase was 20±3.2 IU (N=8-25), and tryptase was 49±36 μg/mL (N<10). Interferon alpha was discontinued in 2 patients because of poor tolerance. Mean follow-up was 60 months. No patient developed a fracture under treatment. In the 8 patients treated with interferon alpha and pamidronate, the mean annual increase in spinal bone mineral density was 12.6%±5.6% and 1.93% in hip bone mineral density. Serum C-terminal telopeptide decreased by 66%, bone alkaline phosphatase decreased by 25%, and tryptase decreased by 34%. In the 2 patients treated with pamidronate alone, mean annual bone mineral density increase was 2.4%±0.1% at the spine and 0%±01% at the hip.

Osteoporosis secondary to mastocytosis mainly affects trabecular bone, and markers of bone remodeling are normal. Combined treatment with low doses of interferon and pamidronate markedly increased bone density.