Difficult Diagnosis in a Patient with Multiple Osteoblastic Thoracic Vertebral Lesions

Abstract

Detection of the underlying neoplasm in a patient with metastasis of unknown origin is a difficult puzzle for an internist to solve. Almost 0.5% to 9% of cancer patients have undetectable primary tumor on admission, and the prognosis of such cases is accepted to be quite poor despite extensive workup for the detection of occult malignancy.1 We hereby present an unusual diagnosis in a patient presenting with multiple osteoblastic metastatic pattern in the axial skeleton.A 64-year-old male applied to our clinic with a chief complaint of progressive increase in back pain and a history of intermittent attacks of fever. His appetite had been good and he gave no history of smoking, alcohol consumption or weight loss. On admission, there was nothing significant on physical examination, but there was Grade 1 prostatic hyperplasia. Hematological parameters, peripheral smear, bone marrow aspiration with biopsy, blood biochemistry, including alkaline phosphatase and calcium, as well as serum tumor markers, were within normal limits. PPD skin test was negative within 48 and 72 hours. Blood and bone marrow cultures were negative for growth of a pathogenic organism. Direct x-ray examination of the thoracic and lumbar vertebrae revealed no abnormality, while 99mTc-MDP bone scintigraphy demonstrated multiple osteoblastic lesions in the 2nd, 8th and 9th thoracic vertebrae, which was also proven by magnetic resonance imaging (MRI), with the additional findings of similar lesions in the 5th and 6th thoracic vertebrae. Further metastatic workup for primary tumor, including lung, gastrointestinal tract, prostate, thyroid and other systems, was negative for evidence of malignancy. Our patient had no history of ingesting raw milk, unpasteurized cheese or dairy products, yet we studied brucella antibody titer owing to sporadic occurrences of brucellosis in particular regions of our country. The serum antibody titer against brucella was suggestively high, being positive in 1/320. Histopathological examination of the biopsy specimen obtained from the involved eighth and ninth thoracic vertebrae revealed "clusters of inflammatory cells without a malignant infiltration." Antimicrobial treatment was composed of ofloxacin per os 200 mg/day and rifampin per os 600 mg/day were instituted promptly with the diagnosis of clinical brucellosis.2 Symptoms, including pain and fever, resolved within two weeks. Ofloxacin plus rifampin therapy was continued for up to six weeks, and then stopped. At the sixth month of follow-up, the patient remained symptom-free, with his control serum brucella antibody titer lowered to 1/80. Subsequent scintigraphic and MRI examinations were free of an osteoblastic lesion and no other skeletal complication of brucellosis was noted.Osteoarticular complications of brucellosis are frequent (25%) and are most commonly located in the sacroiliac joints, with associated sacroiliitis in 72% of patients.3 However, lumbar vertebral involvement is not common (22%) and that of thoracic vertebrae is extremely infrequent (6%), in whi...