Efficacy of denosumab therapy for a 12-year-old female patient with Williams syndrome with osteoporosis and history of fractures: a case report

BACKGROUND: A decrease in bone mineral density is common in patients with Williams syndrome. However, appropriate management for osteoporosis in Williams syndrome patients has not been established. We report the case of a 12-year-old female patient with Williams syndrome, who underwent denosumab treatment for osteoporosis. CASE PRESENTATION: A 12-year-old Japanese female patient with Williams syndrome was shown to have very low bone mineral density. Bone mineral density was evaluated before treatment and at 5, 9, 17, 23, and 29 months of treatment by dual-energy X-ray absorptiometry. After denosumab therapy for 29 months, lumbar and total hip bone mineral density values had increased by 51.6% and 37.6%, respectively. No new fractures occurred during the observation period. CONCLUSIONS: To the best of our knowledge, this is the first experience with denosumab treatment in Williams syndrome patients with osteoporosis. Based on our findings, denosumab may be an effective treatment option for Williams syndrome patients with osteoporosis.