Atypical Osseous Sarcoid: A Case of Multifocal Osteonecrosis Presenting As Back Pain

Summary: Osseous involvement in sarcoidosis is rare,presenting with non-caseating granulomas without bony infarcts. Osteonecrosis that involves three or more different anatomic sites, defined as multifocal osteonecrosis (MFON), is one of the rarest presentations of sarcoid involvement of the bone. We present the case of a 46 year old male with history of ulcerative colitis who presented for a rheumatologic evaluation after an extensive hospitalization prompted by severe back pain with progressive weakness of the lower extremities. The patient was treated for Guillain Barre Syndrome (GBS) and also received steroids for possible active ulcerative colitis. Due to unclear etiology of his back pain, the patient underwent imaging showing numerous contrast enhancing lesions in multiple vertebrae. Malignancy was excluded via bone marrow biopsy and these were left for outpatient follow up. During an outpatient work up, the patient was found to have mediastinal lymphadenopathy. Lymph node biopsy was consistent with a new diagnosis of sarcoidosis. MRI performed to further assessment of the spine was suspicious for MFON. Angiotensin converting enzyme (ACE) levels and Lysozyme were negative, and the patient did not appear to have active sarcoid in other organ systems. To the best of our knowledge, there is only one prior case reported in the literature of multifocal avascular necrosis, as this appears to be an atypical presentation for sarcoid involvement in bone.