Osteopetrosis masquerading as hip osteoarthritis
A 41-year-old female reported right hip pain for one month, previously diagnosed as osteoarthritis. Patient had no history of fracture, bone pain, or trauma-related injuries. X-rays, magnetic resonance imaging and bone scans were taken of the right femur, hip, and lumbar spine which demonstrated diffuse abnormal bone sclerosis with cortical thickening. Spine X-ray which revealed the classic rugger-jersey appearance consistent with osteopetrosis in the setting of normal parathyroid hormone ruling out hyperparathyroidism.

Whole body scan revealed diffuse process of her disease with abnormally increased uptake in almost all her bones especially at the ends of long bones. Laboratory examination of the patient demonstrated alkaline phosphatase 90 IU/L, vitamin D25 18.7 ng/ml, calcium 8.5 mg/dl, ionized calcium 4.5 mg/dl, PTH 42 pg/ml, protein 7.6 g/dl, albumin 4.2 g/dl, CA 15-3 (<8 U/ml), CA27-29 (<12 U/ml), CEA (1.3 ng/ml). Given that her parathyroid harmone (PTH) was not elevated and she had low-normal calcium, hyperparathyroidism was unlikely.

Her normal alkaline phosphatase and mildly low vitamin D25 also made osteomalacia unlikely. Serum markers of Acid Phosphatase Prostatic, CA 27-29, CA 15-3, and CEA were negative ruling out malignancy. Patient had no other signs of symptoms of multiple myeloma as well as no protein-albumin gap. The diagnosis of osteopetrosis was made.

Although this patient presented with localized pain in her right hip, imaging found that her disease was diffuse and extensive. The patient was seen in hospital by orthopedic surgery who recommended outpatient total right hip replacement given the severity of bone changes and uncontrolled pain. Patient was discharged on an oxycontin taper with percocet as needed as well with osteopetrosis require special considerations and close outpatient follow-up.

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