RF30 | PSAT134 Autosomal Dominant Hereditary Multiple Osteochondromas Misdiagnosed As Paget's Disease of Bone

BACKGROUND: Autosomal dominant hereditary multiple osteochondromas is a rare genetic disorder with variable clinical manifestations. We present the case of a patient misdiagnosed with Paget's disease of bone found to have hereditary multiple osteochondromas. CLINICAL CASE: We present a 55-year-old male with history of chronic back and hip pain who presented to endocrinology clinic for evaluation of Paget's disease of bone. He was diagnosed with Paget's disease at age 16 after a bike accident resulting in knee pain where a "knot" was removed from his knee. He reported multiple "knots" in bones throughout adulthood but never sought treatment. He had history of elevated alkaline phosphatase on prior chemistries. He developed debilitating back, hip, and thigh pain resulting in immobility and suffered vertebral osteomyelitis from MRSA requiring laminectomy at age 52. On physical exam, massive maxillary and mandibular tori were noted along with bilateral cataracts and decreased muscle strength in upper and lower extremities. He underwent evaluation by oral surgery for extensive tooth decay and was recommended for extraction of teeth #12, 14, 15, and 17 with restorative needs for teeth #2, 4, 5, 13, 28, 30, 32. Labs notable for serum calcium 10.1 (ref: 8.4-10.5 mg/dl), phosphorus 4.2 (ref: 2.3-4.7 mg/dl), magnesium 1.8 (ref: 1.6-2.6mg/dl), PTH 34 (ref: 16-77 pg/ml), 25-OH Vit D 28 (ref: 25-80 ng/ml), 1,25 dihydroxyvitamin D 45.9 (ref: 19.9-79.3pg/ml), alkaline phosphatase 199 (ref: 40-150 unit/L), bone-specific alkaline phosphatase 52.5 (ref: 6.5 - 20.1 mcg/L). 24-hr urine calcium 0.06 g/24hr (ref: 0.04-0.35) from an 850ml urine volume. Procollagen type 1 n-terminal propeptide 179 (ref 22-105 UG/L). Prior MRI right hip showed "abnormal appearance of pelvic bony ring and proximal femurs with heterogenous marrow signal and cortical thickening suspicious for Paget's disease", as well as a 1.2cm circumscribed cystic focus within proximal right femoral diaphysis. Prior bone scan demonstrated diffusely uptake in pelvis, uptake in proximal right femur, focally intense uptake in L5 vertebrae. Plain film imaging demonstrated severe diffuse degenerative changes in cervical, thoracic and lumbar vertebrae and sessile osteochondromas arising from both scapulae, mild thoracic levoscoliosis. Genetic testing demonstrated loss-of-function mutation in the EXT-1 gene, diagnostic of hereditary multiple osteochondromas. Currently, there are no FDA-approved treatments for osteochondromas though studies involving biologic therapy are ongoing. This patient was referred to orthopedic oncology and OMFS for dental extraction and decision for conservative treatment with observation. CONCLUSION: This case demonstrates how the rare entity of hereditary multiple osteochondromas can have variable clinical presentations leading to its misdiagnosis and highlights the need for ongoing research into non-surgical treatment options. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m., Monday, June 13, 2022 12:36 p.m. - 12:41 p.m.