Pregnancy and Lactation-Associated Osteoporosis Successfully Treated with Romosozumab: A Case Report

Pregnancy- and lactation-associated osteoporosis (PLO) is a rare type of premenopausal osteoporosis that occurs mainly in the third trimester or immediately after delivery; one of its most common symptoms is back pain caused by a vertebral fracture. The pathogenesis of PLO is unclear, and there is no accepted consensus regarding the treatment of PLO. Although treatments with drugs such as bisphosphonate, strontium ranelate, denosumab, and teriparatide were reported, there is no report of a patient with PLO treated with romosozumab. We present the first case of a patient with PLO treated with romosozumab following 4-month teriparatide treatment. A 34-year-old primiparous and breastfeeding Japanese woman experienced severe low back pain 1 month postdelivery. She was diagnosed with PLO on the basis of low bone marrow density (BMD) and multiple vertebral fractures with no identified cause of secondary osteoporosis. She was treated with teriparatide injection for 4 months, but the treatment was discontinued because of the patient feeling severe nausea after every teriparatide injection and the appearance of new vertebral fractures. Thereafter, we used romosozumab for 12 months. After the romosozumab treatment, her BMD was increased from the baseline by 23.6% at L1–L4, 6.2% at the femoral neck, and 11.2% at the total hip. Treating PLO with 12-month romosozumab after 4 months of teriparatide injection remarkably increased the BMD of the lumbar spine, femoral neck, and total hip without subsequent fracture. Romosozumab has potential as a therapeutic option to improve the BMD and reduce the subsequent fracture risk of patients with PLO.