Shuangfang Zhu Yaqi Dong songfeng Xu Yuxuan Wei Jingyang Huang Shaoli Zhen Laihua Fu Corresponding author

【Abstract】Mycobacterium abscessus spondylitis is clinically rare， the test results and imaging， PET-CT and other findings are not clearly characterized， pathological findings can assist in the diagnosis， and active bacterial culture and identification are still needed to clarify the diagnosis. If early detection， early diagnosis and early treatment can be achieved， it is of great significance to the prognosis of patients. In this case， an elderly female with low back pain as the main complaint， no chills and fever， no night sweats and weakness， no significant elevation of leukocytes and inflammatory indexes， chest CT examination suggesting interstitial pneumonia， no significant abnormalities of tumor screening indexes; T-cell spot test results of tuberculosis infection suggesting negative; preoperative imaging examination alerting metastases; PET-CT examination suggesting thoracic spine compression fracture with high possibility of paravertebral infection; perfect The patient underwent posterior thoracic spinal canal decompression， thoracic 8 mass resection + artificial vertebral body and internal fixation with bone graft under general anesthesia; the postoperative pathological results indicated "tendency" of Mycobacterium tuberculosis infection with PAS（-） and antacid staining （+）. Combined with the patient's pathological results， the patient was discharged from the hospital and started anti-tuberculosis medication; more than 3 weeks after surgery， the patient was treated with wound dressing and three consecutive secretions were taken for bacterial culture and identification by VITEK MS IVD V3.0 mass spectrometer， and the results were all suggestive of Mycobacterium abscessus， and finally the causative organism was identified as Mycobacterium abscessus.

【Key words】Atypical mycobacteria;Nontuberculous mycobacteria; Bacterial infections;Spondylitis;Diagnosis

【中圖分类号】S855.1+2  【文献标识码】A  【文章编号】1673-9026（2021）06-436-02

The patient， a 61-year-old female， was admitted to Shenzhen Hospital of Cancer Hospital of Chinese Academy of Medical Sciences on June 02， 2020 as an outpatient due to "low back pain for 3 months， aggravated for more than 1 month". The patient was admitted to Shenzhen Hospital of Chinese Academy of Medical Sciences on June 02， 2020. The patient was diagnosed with type 2 diabetes mellitus in 2017， during which he was given metformin and insulin to control blood glucose on his own， with irregular medication; the patient was diagnosed with dermatomyositis in 2019， during which he was given oral prednisone and cyclosporine for symptomatic treatment， with regular medication， and was admitted to the hospital with interstitial pneumonia caused by lung involvement. He denied the history of hypertension， coronary heart disease， renal disease， etc.; denied the history of hepatitis， tuberculosis， typhoid， malaria and other infectious diseases; denied the history of surgery， major trauma; denied the history of blood transfusion; denied the history of drug and food allergy; born and grew up in Ningde City， Fujian Province， and has been living in Shenzhen for the past six months， with no history of travel to high-risk areas， no history of exposure to high-risk people， negative nucleic acid test results， and denied the history of exposure to special chemicals and radioactive substances. He has a family history of tumor， his brother had pancreatic cancer and passed away， and his sister had lung cancer. He has no smoking or alcoholic habits.Admission physical examination： body temperature： 36.2℃， heart rate： 90 beats/min， respiration： 19 breaths/min， blood pressure： 154/83mmHg， height： 156cm， weight： 50Kg， BSA： 1.47m2， KPS： 80 points. He had clear consciousness， fluent speech， cooperative physical examination， wheelchair-assisted admission， marked limitation of thoracolumbar activities， difficulty in turning over， pressure pain （+） and percussion pain （+） in the spinous process and paraspinal muscles of the thoracic 5-11 vertebrae， radiating pain in the bilateral rib area， general activity of both lower limbs， muscle strength grade IV in both lower limbs， no significant abnormal sensation， no abnormal muscle tone， normal knee reflex and ankle reflex， and no pathological signs were elicited. There was no enlargement of superficial lymph nodes throughout the body; the heart was in rhythm， and no murmur was heard in each valve auscultation area; the breath sounds in both lungs were coarse， and no obvious dry and wet rales could be heard; the abdomen was soft， with no pressure pain or rebound pain， and the bowel sounds were normal， and there was no edema in both lower limbs.Laboratory tests on admission： Blood count： WBC： 8.93 x 109/L， NEUT： 6.94 x 109/L， LYM： 0.70 x 109/L， Hb： 91g/L， PLT 495 x 109/L， C-reactive protein assay： 20.09mg/L; Calcitoninogen assay： PCT 0.024ng/ml Fasting blood glucose 8.12 mmol/L， no significant abnormalities in tumor screening index; TB infection T cell test： TB infection T cell spot test result： negative; TBNK lymphocyte subpopulation： B cells/lymphocytes 20%. MRI of the thoracic spine was performed on admission： pathological fracture with local soft tissue formation due to metastases in the 7th-8th vertebrae of the thoracic spine; CT of the thoracic spine suggested： about the 8th thoracic spine lesion， the nature of which is to be determined， to be alert to malignancy， traumatic fracture with a little surrounding hematoma is also difficult to completely exclude; whole body bone imaging + local imaging suggested： the 8th thoracic spine increased radioactivity， considering the changes after compression fracture， and it is recommended to combine with clinical exclusion of malignant lesions PET-CT examination suggests： new comminuted fracture of T8 vertebrae， with surrounding hypermetabolic soft tissue swelling， involving T7-9 vertebrae， considering the possibility of compression fracture of thoracic vertebrae due to osteoporosis and paravertebral infection， combined with pathology if necessary; 2. Bilateral hair around the elbow joint， proximal right forearm， distal left forearm， left palm and thumb， left posterior chest wall soft tissue swelling， multiple slightly The hypodense shadow with increased metabolism is not consistent with malignant tumor manifestation， please consider with the history of dermatomyositis， and suggest a comprehensive hospital consultation.After perfecting preoperative preparation and excluding contraindications to surgery， the patient underwent posterior thoracic decompression， thoracic 8 mass excision + artificial vertebral body， and internal fixation with bone graft under general anesthesia， and the operation went smoothly; follow-up is still continuing. Postoperative pathological tissue results： （1） （thoracic 7， thoracic 8 right paravertebral mass）， （2） （thoracic 8 vertebral lesion） cartilage， bone and fibrous tissue， visible dead bone and inflammatory granulation tissue， with inflammatory cell infiltration， a large number of histiocyte aggregates and multinucleated giant cell reaction， there is no clear evidence of malignancy， it is recommended to combine with clinical further diagnosis and treatment. Immunohistochemical results showed：AE/AE3（-），Ki-67（10%），CK18（-）， CD68（3+）， CD163（3+）.2020.06.30 Supplementary pathological diagnosis： （1）（right paravertebral swelling of thorax 7 and 8）， （2）（thorax 8 vertebral body lesion） combined with special staining results， inclined to Mycobacterium tuberculosis infection， it is recommended to combine with clinical Further clarification. Special staining results showed PAS （-）， antacid staining （+）. Bacterial culture and identification： more than 3 weeks after surgery， the patient's surgical incision on the chest and back appeared red and swollen， and a small amount of purulent discharge was visible; three smears of antacid staining of wound secretions were examined： microscopic examination of antacid staining： antacid-positive bacilli were found; the results of the VITEK MS IVD V3.0 mass spectrometer were all suggestive of growth of Mycobacterium abscessus （++++）; WBC： 9.30 x 109/ L， NEUT： 7 L，NEUT：7.67 x 109/L，LYM：0.59 x 109/L，Hb：89g/L，PLT 506 x 109/L，C-reactive protein assay： 34mg/L; Calcitoninogen assay： 0.063ng/ml.

Figure A - B： the positive and lateral DR of the thoracolumbar spine： T8 vertebral body compressed and flattened， respectively; Figure C-E： the horizontal， sagittal and coronal views of the CT scan of the thoracic spine， respectively： about the 8th thoracic vertebral body showed a comminuted compression fracture， with uneven thickening of the soft tissue shadow bilaterally， the right side was obvious， the maximum thickness was about 1.4 cm， the length was about 3.5 cm， and there seemed to be a cystic area inside， which affected the right pedicle and protruded into the spinal canal， with The adjacent dural sac was compressed. The nature of the lesion in the approximately 8th thoracic vertebra is to be determined， and it is important to be alert for malignancy， and it is difficult to completely exclude traumatic fractures with a small surrounding hematoma. Figure F- H： PET-CT： new comminuted fracture of T8 vertebra with surrounding hypermetabolic soft tissue masses involving T7-9 vertebrae， respectively， considered to be a thoracic compression fracture with paravertebral infection due to osteoporosis. Figure I： Intraoperative pictures of the road thoracic spinal canal decompression， thoracic 8 mass resection + artificial vertebral body and internal fixation with bone graft.Figure J-K： postoperative frontal and lateral DR of the thoracic spine： good position of internal fixation; Figure L： after the patient's wound removal 10 days after surgery： the incision healed OK， and the dressing was dry and clean; Figure M： the patient's wound 3 weeks after surgery： the thoracic back wound was obviously red and swollen， and the lower end of the wound healed poorly， with fluid accumulation， rupture and oozing， and a little purulent secretion was visible on the dressing.

III. Discussion

Nontuberculous mycobacteria （NTM） refers collectively to a large group of mycobacteria other than Mycobacterium tuberculosis complex （including Mycobacterium tuberculosis， Mycobacterium bovis， etc.） and Mycobacterium leprae. It is a group of conditionally pathogenic bacteria widely present in natural and anthropogenic environments， mainly bound to soil， water and biofilms [1]. In recent years， infections caused by NTM have been on the rise globally and are difficult to treat due to the complexity of identification of these bacterial subspecies， inherent resistance to many common antibiotics， and lack of antibiotic susceptibility testing [2]. Mycobacterium abscessus is one of the fast-growing， multidrug-resistant nontuberculous mycobacteria of NTM [3]; clinically， it is most commonly found in the lungs [4]， but can also occur in the skin， soft tissues， bones， central nervous system， bacteremia， eyes， and immunocompromised patients [5-7]; the virulence， transmission， and environmental persistence of this group of bacteria remain many unanswered questions [8]， are extremely harmful， take a long time to treat long， causing a serious disease burden and economic burden to patients and reducing their quality of life and well-being.

In clinical practice， the initial diagnosis of Mycobacterium tuberculosis infection is not difficult， and the result can be obtained by antacid staining of focal tissue or secretions. However， the term "Mycobacterium bovis" is a generic term for a large group of bacteria， and antacid staining still cannot clearly identify Mycobacterium tuberculosis from non-tuberculous Mycobacterium bovis， nor can it distinguish between the various subgroups of Mycobacterium bovis， and even if the antacid staining result is positive， the diagnosis is still not clear and effective symptomatic treatment is not available. Therefore， the significance of pathology in recognizing and differentiating the histology of such lesions is self-evident for the early diagnosis of such diseases. Bacterial culture and identification should be actively considered when pathological findings do not allow for a definitive diagnosis [9]. In this case， the patient's postoperative pathology suggested a "tendency" to Mycobacterium tuberculosis infection with PAS （-） and antacid staining （+）. In combination with the patient's pathological results， the patient was discharged from the hospital and started anti-tuberculosis medication; more than 3 weeks after surgery， the patient was treated with wound dressing and three consecutive secretions were taken for bacterial culture and identification by VITEK MS IVD V3.0 mass spectrometer， and the results were all suggestive of Mycobacterium abscessus， which finally made it clear that the causative organism was Mycobacterium abscessus.

Through the diagnosis and treatment of this case， we have gained some experiences： 1. Clinicians should improve disease awareness of NTM to achieve early detection， early diagnosis and early treatment to improve patient prognosis; 2. For patients who take hormones and immunosuppressants for a long time and have complicated underlying diseases such as diabetes， connective tissue diseases and osteoporosis， they should be alert to the possibility of NTM when bone unexplained lesions appear; 3. The possibility of NTM needs to be identified at the same time when bone unexplained lesions are suspected of bone tuberculosis， infection and tumor; 4. Once diagnosed， it should be treated actively and， if necessary， in a multidisciplinary manner to improve the treatment effect and the quality of life of patients.

In conclusion， Mycobacterium abscessus spondylitis is clinically rare， the test results and imaging， PET-CT and other findings are not clearly characterized， pathological findings can assist in the diagnosis， and active bacterial culture and identification are still needed to clarify the diagnosis. If early detection， early diagnosis and early treatment can be achieved to reduce misdiagnosis and mistreatment， it is of great significance to the prognosis of patients.

Conflict of interest All authors declare no conflict of interest

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National Cancer Center / National Clinical Research Center for Cancer / Cancer Hospital & Shenzhen Hospital，Chinese Academy of Medical Sciences and Peking Union Medical College， Shenzhen，Department of Orthopedics;