SAT-773 Primary Hyperparathyroidism in a Patient with Osteogenesis Imperfecta Type I and Osteoporosis

Abstract Disclosure: M. Joven: None. T. Brown: None. G. Gottesman: None. Introduction: Osteogenesis Imperfecta (OI), often caused by defective COLIA1 or COLIA2, results in skeletal fragility. It may be associated with low bone mass and osteoporosis hence fracture rates which often decline post-pubertal years, rise again after menopause. Coexisting conditions such as primary hyperparathyroidism have been reported but are limited. CASE REPORT An 81-year-old woman with OI type I presented for evaluation of hypercalcemia. OI type I was diagnosed at the age of 8 years following her father’s diagnosis of OI type 1. She reports ∼ 30 fractures throughout her life, including a clavicular fracture when she was born and subsequent long bone and vertebral fractures throughout her life, some of which were managed surgically. She was diagnosed with osteoporosis after menopause in her early 50s and was started on risedronate. Around the age of 65 years, she sustained a low trauma tibial fracture thought to be “atypical” after 10 years of risedronate therapy. She was treated with two years on teriparatide, then started denosumab a year later, which she continued for the past 10 years. She was noted to have mild serum calcium elevations for the past 12 years ranging from 9.4 to 10.6 mg/dl (ref, 8.4-10.2). Alkaline phosphatase, phosphorus and vitamin D were normal. PTH (some concurrently measured with serum calcium) were elevated from 62.3-112.5 pg/ml (ref, 8.5-84.9). Examination was notable for blue grayish sclerae, profound hearing loss, and skin laxity. Neck ultrasound to assess multinodular goiter did not reveal suspicious parathyroid lesions. Additional imaging to localize cause of primary hyperparathyroidism was not pursued as surgery was not contemplated. DISCUSSION Primary hyperparathyroidism, often from a parathyroid adenoma, has been reported in the literature in patients with OI. This rare co-existence has been reported with most cases in their early postmenopausal period. Only a few studies have measured PTH as in this case. Both conditions on top of postmenopausal osteoporosis result in low bone density and poor bone quality resulting in fragility fractures. There is limited data in managing these concurrent conditions including pursing a definitive surgical treatment of primary hyperparathyroidism. Although some treatments for osteoporosis and OI overlap, we have limited, long-term data on denosumab use. CONCLUSION Primary hyperparathyroidism in OI type I and osteoporosis can co-exist. Routine measurement of calcium should be done in patients with OI as these conditions can occur and the diagnosis and opportunity for treatment can be missed. Additional studies are needed to establish this concurrence. Presentation: Saturday, July 12, 2025