MON-505 An Atypical Case of Osteoporosis Related to Pregnancy and Lactation

Abstract

Background: Osteoporosis is rare in premenopausal patients without predisposing risk factors. A few case reports have described vertebral or hip fractures in young females due to pregnancy and lactation associated osteoporosis (PLAO). A proposed mechanism for PLAO is maternal bone resorption during pregnancy due to inadequate calcium stores to meet both maternal and fetal demands as well as hormone mediated trabecular bone demineralization to supplement calcium in maternal milk. We present a case of PLAO in a postpartum patient who suffered multiple atraumatic fractures of her vertebrae, clavicle, rib, and pelvic rami. To our knowledge, this is a unique combination of fractures that has not been previously reported. Clinical Case: A 38 year-old gravida 2 para 2 female presented for evaluation of back pain that started two months after she delivered her second child and while breastfeeding. Relevant past medical history included left hip chondrosarcoma that was treated with hemipelvectomy five years prior, with a concomitant diagnosis of right hip fracture while breastfeeding her first child. Subsequent imaging had been negative for chondrosarcoma recurrence or metastases. Prior to her first pregnancy, there was no history of trauma, glucocorticoid use, personal or family history of fracture, smoking, or alcohol use. Spinal imaging revealed vertebral compression fractures at T9, T12, and L5. Bone biopsies were negative for malignancy. Retrospective review of imaging after the first delivery and during lactation revealed incidental right clavicular and left rib fractures. Evaluation for secondary causes of osteoporosis, including total corrected calcium, ionized calcium, alkaline phosphatase, parathyroid hormone, thyroid-stimulating hormone, serum protein electrophoresis, and 24-hour urine cortisol were all normal. 25-OH vitamin D level was 30 (30-100 ng/mL), bone-specific alkaline phosphatase (BSAP) was elevated at 21.6 (range 5.3-19.5 mcg/L), and collagen type I c-telopeptide (sCTx) was 342 (range 60-650 pg/mL). DXA revealed Z scores of -2.9, -3.1, and -2.6 at the lumbar spine, femoral neck, and total hip respectively. Calcium carbonate-vitamin D 1000 mg-400 IU twice daily and breastfeeding cessation were recommended, followed by zoledronate 5mg IV. Three months later, BSAP and sCTx had decreased to 11.8 and 101 respectively. The patient has since been fracture free. Discussion: PLAO is exceedingly rare. Initial manifestations may include low trauma or atraumatic fractures of non-weight-bearing sites such as the clavicle. The diagnosis may be delayed due to the initial presentation of non-specific pain in an otherwise healthy female without risk factors. Increasing awareness and pursuing further research into the etiology of this disorder could lead to the development of appropriate guidelines for prevention of fractures in these patients.