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Year : 2018  |  Volume : 7  |  Issue : 1  |  Page : 104-106

Mycobacterium chelonae osteomyelitis presenting as a mycobacterial spindle cell pseudotumor

1 Department of Obstetrics and Gynaecology, Stoke Mandeville Hospital, Aylesbury, UK
2 Department of Infectious Disease, Churchill Hospital, Oxford, England, UK
3 Department of Infectious, Nuffield Orthopaedic Centre, Oxford, England, UK
4 Department of Histopathology, Nuffield Orthopaedic Centre, Oxford, England, UK

Date of Web Publication7-Mar-2018

Correspondence Address:
Dr Victoria Thwaites
Department of Obstetrics and Gynaecology, Stoke Mandeville Hospital, Aylesbury
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijmy.ijmy_166_17

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We report a case of an 88-year-old man with osteomyelitis of the right ankle, with histopathology demonstrating a Mycobacterium spindle cell pseudotumor. The Mycobacterium contained in this spindle cell pseudotumor was Mycobacterium chelonae. M. chelonae spindle cell pseudotumors are rare and have only been reported twice previously in the literature. Similarly, M. chelonae presenting as the pathogen in bone infection is rare. Due to this unusual presentation of M. chelonae, the antibiotic rationale was based largely on case reports and consisted of imipenem, clarithromycin, and linezolid. Antibiotic complications were experienced by the patient. Despite a renally adjusted dose of imipenem, the patient experienced imipenem toxicity and his antibiotics were modified to tigecycline and clarithromycin. Although his symptoms were clinically resolving, the patient sadly passed away before completing treatment.

Keywords: Mycobacterium chelonae, osteomyelitis, spindle cell pseudotumor

How to cite this article:
Thwaites V, Colston J, Lomas-Cabeza J, Orosz Z. Mycobacterium chelonae osteomyelitis presenting as a mycobacterial spindle cell pseudotumor. Int J Mycobacteriol 2018;7:104-6

How to cite this URL:
Thwaites V, Colston J, Lomas-Cabeza J, Orosz Z. Mycobacterium chelonae osteomyelitis presenting as a mycobacterial spindle cell pseudotumor. Int J Mycobacteriol [serial online] 2018 [cited 2019 Dec 9];7:104-6. Available from: http://www.ijmyco.org/text.asp?2018/7/1/104/226775

  Introduction Top

The presentation of Mycobacterium chelonae is unusual in the setting of bone infection[1],[2],[3],[4] and the presentation of M. chelonae as a spindle cell pseudotumor even more so.[5] The setting of this unusual case presentation is documented alongside the antibiotic therapy used and the rationale behind this. It highlights complications to this treatment, namely imipenem toxicity, despite renal dose adjustment.

  Case Report Top

An 88-year-old man presented with a 6-week history of pain in his right ankle and erythema over the right lower leg. The lateral malleolus and lateral part of the calcaneum were swollen and tender, and he was unable to weight-bear on the right foot. He also reported a history of weight loss, change in bowel habit, and loss of appetite over the previous 6 months. He had an extensive medical history: chest wall melanoma excised the year before; atrial fibrillation; type 2 diabetes mellitus; gout; chronic kidney disease; a coronary artery bypass graft insertion; and right total knee replacement. The patient also reported an allergy to penicillin.

A magnetic resonance imaging of the right foot showed a distal fibular lytic lesion, suggestive of osteomyelitis, extensive cellulitis with peroneal tenosynovitis, and a calcaneal lesion with features of a bone infarct.

A bone biopsy of the right ankle initially reported acid-fast bacilli, with histology showing evidence of a mycobacterial spindle cell pseudotumor [Figure 1] and [Figure 2]. The bone biopsy sample demonstrated rapid mycobacterial growth and was referred to the Mycobacterial Reference Laboratory, where the isolate was identified as M. chelonae (through polymerase chain reaction-based rapid identification).[6]
Figure 1: Between bone trabeculae, spindle cells are forming small nodules and fascicles. There is focal accumulation of lymphocytes and eosinophilic granulocytes are also seen. No caseous necrosis or Langhans type giant cells are seen (H and E, ×100)

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Figure 2: The spindle cells have ovoid, slightly elongated nuclei without pleomorphism or mitotic activity (H and E, ×100). Inset: Ziehl–Neelsen staining showing scattered purple rod-like bacilli (arrows) (Ziehl–Neelsen stain, ×400)

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M. chelonae is typically associated with immunocompromise, and computed tomography of the chest, abdomen, and pelvis was performed. This found an appendix mucocele and new lung nodules in the right lung but no definitive evidence of malignancy.

The initial empirical choice of antibiotics was imipenem 250 mg three times a day (a renally adjusted dose due to the patient's estimated glomerular filtration rate of 35), clarithromycin 500 mg twice a day, and co-trimoxazole 960 mg twice a day. Imipenem is the preferred carbapenem in M. chelonae infection.[2]

Following receipt of the Reference Laboratory sensitivities (reported sensitivity to amikacin, clarithromycin, and linezolid with resistance to cefoxitin, co-trimoxazole, ciprofloxacin, moxifloxacin, and doxycycline), the patient was switched to imipenem, clarithromycin, and linezolid. Previous studies have found that clarithromycin in combination with linezolid is clinically effective in immunocompromised patients with cutaneous M. chelonae.[7] The patient was sent home with outpatient antimicrobial therapy and regular blood monitoring.

Several complications were encountered with this choice. Most significantly, despite a renally adjusted dose of imipenem, the patient was re-admitted 12 days after starting treatment with confusion. Mild diffuse encephalopathy was diagnosed on electroencephalogram but no seizure activity. These symptoms did not reoccur after imipenem was stopped. Second, the patient began to experience myelosuppression secondary to linezolid (after 12 days of treatment).

Following his readmission, the patient was switched to a combination of tigecycline and clarithromycin. Tigecycline has been reported as improving outcomes as part of a multidrug regimen to treat M. chelonae.[8]

There is no firm evidence upon which to base the duration of treatment in cases of osteomyelitic M. chelonae. Previous case reports have documented mycobacterial spindle cell pseudotumor caused by Mycobacterium intracellulare that took 2 years of antibiotic treatment to resolve.[9]

The literature suggests that along with antibiotics, surgical intervention is vital to treating M. chelonae bone infection. However, given the patient's extensive medical history, he was not believed to be fit for surgery, and therefore, debridement of the bone was not performed.

Clinically, the inflammation of the ankle had begun to subside before readmission, and the patient's symptoms continued to improve with tigecycline and clarithromycin [Figure 3] although the patient's inflammatory markers remained static.
Figure 3: Patient's right ankle, following 10 days of tigecycline and clarithromycin

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After 16 days on this combination of antibiotics, the patient became hypotensive and tachycardic and sadly passed away, with the cause of death found to be a combination of restrictive cardiomyopathy and multiorgan failure. The exact nature of the underlying immunosuppressive pathology remains unknown.

  Discussion Top

Mycobacterial spindle cell pseudotumors are benign lesions that present histologically as spindle-shaped histiocytes containing acid-fast bacilli. They are most commonly caused by Mycobacterium avium and Mycobacterium tuberculosis[5] and usually present in skin, lungs, eyes, and soft tissue.[1] The case presented here is unusual in two respects. The Mycobacterium spindle cell pseudotumor was formed by M. chelonae, a finding that has only been reported twice previously in the literature.[5] Second, M. chelonae presenting in bone has only been reported in nine cases in the literature.[1],[2],[3]

Spindle cell pseudotumors are almost always associated with immunodeficiency: a review of Mycobacterium pseudotumor cases found that of the 23 cases of Mycobacterium spindle cell pseudotumors in the literature, 21 patients had immunosuppression either as a result of HIV/AIDs, immunosuppressive therapy, or diabetes.[5]

Given the patient's history of melanoma, bone metastases were among the initial differential diagnoses. The literature reports that spindle cell pseudotumors are often mistakenly diagnosed radiologically as malignant lesions, for example, sarcomas, schwannomas or histiocytomas, until biopsy confirms otherwise.[9]

Carbapenems are known to lower seizure thresholds and can cause confusion. Imipenem is primarily renally excreted, and therefore, dose adjustment in kidney failure is recommended to limit side effects. In this case, however, side effects occurred despite renal adjustment of the imipenem dose, which resolved on discontinuation of the treatment.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Talanow R, Vieweg H, Andresen R. Atypical osteomyelitis caused by Mycobacterium chelonae-A multimodal imaging approach. Case Rep Infect Dis 2013;2013:528795.  Back to cited text no. 1
Rahman I, Bhatt H, Chillag S, Duffus W. Mycobacterium chelonae vertebral osteomyelitis. South Med J 2009;102:1167-9.  Back to cited text no. 2
Oelberg DA, Mendelson J, Miller MA, Dascal A. Disseminated Mycobacterium chelonae infection presenting as progressive multifocal osteomyelitis: Report of two cases and a review of the literature. Can J Infect Dis 1994;5:28-32.  Back to cited text no. 3
Al-Knawy M, Bosch W, Garner H, Mirsaeidi M, Cawley J, Murray P, et al. A descriptive analysis of nontuberculous mycobacterial infections (NTM) of the upper extremity. Int J Mycobacteriol 2015;4:37-8.  Back to cited text no. 4
  [Full text]  
Sfeir M, Soave R, Van Besien K, Satlin M, Jenkins S, Westblade L, et al. Mycobacterial spindle cell pseudotumor: Epidemiology and clinical outcomes. Open Forum Infecti Dis 2016;3:563.  Back to cited text no. 5
Brown-Elliott BA, Philley JV. Rapidly growing mycobacteria. Microbiol Spectr 2017;5:703-4.  Back to cited text no. 6
Parize P, Hamelin A, Veziris N, Morand PC, Guillemain R, Lortholary O, et al. Induction therapy with linezolid/clarithromycin combination for Mycobacterium chelonae skin infections in immunocompromised hosts. J Eur Acad Dermatol Venereol 2016;30:101-5.  Back to cited text no. 7
Wallace RJ Jr., Dukart G, Brown-Elliott BA, Griffith DE, Scerpella EG, Marshall B, et al. Clinical experience in 52 patients with tigecycline-containing regimens for salvage treatment of Mycobacterium abscessus and Mycobacterium chelonae infections. J Antimicrob Chemother 2014;69:1945-53.  Back to cited text no. 8
Ismail I, Carey M, Trotter S, Kunst H. Mycobacterial spindle cell pseudotumour of the brain in a patient with sarcoidosis. BMJ Case Rep 2015;2015. pii: bcr2014206171.  Back to cited text no. 9


  [Figure 1], [Figure 2], [Figure 3]

This article has been cited by
1 Imipenem/linezolid
Reactions Weekly. 2018; 1697(1): 189
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