Pathological features of Brucella spondylitis: A single-center study

To explore the pathological features of Brucella spondylitis (BS) under the optical microscope, thus providing pathological references for the diagnosis.We retrospectively analyzed 70 BS patients (42 males and 28 females, mean age 52.01 ± 10.77 [20-74] years) admitted in the Department of Spine Surgery, the General Hospital of Ningxia Medical University, from January 2013 to December 2020. Their medical history, clinical manifestations, laboratory test results, imaging findings and bacteriological culture results were collected. Among them, 5, 5, 43, 4 and 13 cases demonstrated involvement into the cervical vertebra, thoracic vertebra, lumbar vertebra, thoracolumbar vertebra and lumbosacral vertebra, respectively. Notably, L4 showed pathology in 32 cases. Pathological features of BS were analyzed by H&E staining of granulation tissues, sclerotic bones, sequestrums, and intervertebral discs.42 cases underwent bacterial culture, of which 4 were positive, and the positive rate of bacterial culture was only 9.5%. The highest Vas score was 7, the lowest was 4, and the average was 5.76 ± 0.89. The highest CRP was 153 mg/L, the lowest was 0.98 mg/L, and the average was 30.98 ± 33.79 mg/L. The highest ESR is 112 mm/h, the lowest is 5 mm/h, and the average is 49.34 ± 27.73 mm/h. Under the optical microscope, BS manifested acute or chronic inflammation. Acute inflammatory features included neutrophil and eosinophil infiltration, necrosis, and abscesses, while chronic inflammatory features included lymphocyte, plasma cell, fibrous tissue and monocyte infiltration, hyaline degeneration, angiogenesis and hyperplasia of other tissues. Other features included vasodilation, hemorrhage, granulomas and multinucleated giant cell infiltration. In the present study, chronic inflammation was observed in 25 cases, in-acute-phase chronic inflammation in 45 cases, and acute inflammation in no cases. Pathological features of BS under the microscope included foam cell reaction in 46 cases, histiocytic reaction in 24 cases and eosinophilic abscesses in 6 cases. Eosinophil infiltration was observed in 45 cases (mainly during the acute phase of chronic inflammation) and massive eosinophilic abscesses in 6 cases. Granulation tissue hyperplasia followed inflammatory repair in 25 BS cases, and was generally boosted in the acute phase of chronic inflammation. Multinucleated giant cell infiltration and granulomas were less observed in BS cases, which differed from pathological features of spinal tuberculosis.Chronic inflammation or in-acute-phase chronic inflammation is the main pathological feature of BS, while the single acute inflammation is less observed in BS cases. Foam cell reaction and histiocytic reaction scale up during the acute phase of chronic inflammation, and some BS patients may develop massive eosinophilic abscesses. Granulation tissue hyperplasia, rather than multinucleated giant cell infiltration and granulomas, serve as pathological reference for the differential diagnosis of BS and spinal tuberculosis.