THU470 Blood - Bone Connection? A Case Of A Young Woman With Bilateral Hip Osteonecrosis And Prothrombin Mutation

Abstract

Abstract Disclosure: A. Sliwinska: None. C. Vanek: None. Introduction: Osteonecrosis of the femoral head (ONFH) is a localized bone disease responsible for 10% of total hip replacements in the United States. Although the condition is a separate entity from osteoporosis, it may co-occur representing underlying systemic bone disease. Many risk factors (steroids, trauma, infections, thrombophilia, blood cell dyscrasias) can predispose to ONFH, therefore, diligent evaluation is required to reveal the underlying cause. There are no FDA approved therapies. Here, we present a case of young woman with bilateral osteonecrosis of femoral head who was found to have prothrombin gene mutation, severe osteoporosis, and was successfully treated with PTH analog therapy with abaloparatide. Case Description: 33-year-old Asian female with no past medical history presented to the Endocrinology clinic for a metabolic bone disease assessment. Two years prior, she developed progressive bilateral hip pain which prompted radiographic evaluation, discovering bilateral ONFH. She was managed non-surgically with a 6-month trial of oral alendronate. Worsening pain prompted left hip decompression surgery with stem cell transfer. Patient had no history of fragility fractures nor family history of bone disease. A bone density revealed Z scores of -3.9 and -3.5 in lumbar spine and total hip, respectively. She was taking 2000 IU vitamin D3 and 600 mg of elemental calcium daily. Her blood tests revealed normal basic metabolic panel, normal complete blood count and liver function tests. Calcium was 9.0 mg/dl (ref:8.6-10.2), albumin 4.6 mg/dl (3.5-4.7 mg/dl), phosphorus 4.0 mg/dl (2.4-4.7 mg/dl), PTH of 28 pg/ml (18-88 pg/ml), Vitamin D 25-hydroxy 41.3 ng/ml (30-80 ng/ml), and TSH was 1.66 mIU/L (0.39-4.17 mIU/L). Patient had an infectious, metabolic and rheumatological work-up that was negative. A thrombosis workup showed a heterozygous prothrombin gene (G20210A) mutation. Factor V Leiden mutation was negative. Repeat Hip MRI showed progression of her ONFH with marked bone marrow edema in femoral head bilaterally. Patient was then started on abaloparatide. After 6 months, hip MRI showed marked improvement with no bone marrow edema. Discussion: Osteonecrosis of the femoral head is a complex disease that can affect young individuals. Bilateral ONFH suggests systemic disease and a thorough work-up is necessary. Although the exact mechanism is unclear, it has been hypothesized that thrombin plays a role in bone homeostasis therefore hematologic disorders may predispose patients to both ONFH and osteoporosis. Medical treatment of ONFH, including bisphosphonates, statins, or anticoagulants, have been suggested. Recently the PTH analog, teriparatide, has shown promising results and found to be beneficial in treating osteonecrosis. Our case highlights importance of thorough work-up for patients with bilateral ONFH and successful use of anabolic agent in this population. Presentation: Thursday, June 15, 2023