Introduction

Tuberculosis cases have increased in the past few years due to acquired immunodeficiency syndrome (AIDS) and immigration of people from endemic zones, affecting one-third of the world’s population. After ganglion and kidney affection, osteoarticular tuberculosis is the third form of extrapulmonary tuberculosis. With the reemergence of tuberculosis, more atypical osteoarticular cases are seen. Staphylococcus aureus is usually responsible for osteomyelitis in patients with chronic renal failure. A high grade of suspicion is necessary to diagnose tuberculosis aetiology in a patient affected with chronic monoarthritis with risk factors that present an insidious evolution.

Case report

We report the case of a 55-year-old man who presented with a 15-day history of fever (39°C) and a painful and effused knee, without traumatism. The patient had a history of schizophrenia, high blood pressure, diabetes mellitus, and chronic renal failure secondary to diabetic nephropathy. Physical examination showed a heat and effused knee. Blood test revealed 12.1×109 l−1 leukocytes (82.5 neutrophils, 9.5 lymphocytes), erythrocyte sedimentation rate (ESR) of 121 mm/h, and C-reactive protein (CRP) of 11.8 mg/dl. Radiographs of the knee were considered normal (Figs. 1, 2). Knee puncture was performed and joint liquid showed 9,600 cells (95% neutrophils), 44 g/l proteins and 93 mg/dl glucose. Ziehl-Nielsen and Gram stains were negative. We started intravenous antibiotic treatment with vancomycin, but after 15 days of therapy, the patient remained febrile and the inflammatory signs persisted. A bone scan with technetium 99m-labelled leukocytes showed an important uptake by the external tibial plateau area (Fig. 3). A CT scan revealed a cortical lytic lesion on the external margin of the tibial plateau, with an important soft tissue component. MRI was performed and demonstrated an extent soft tissue lesion (5×5 cm2) on the external aspect of the knee, extending and destructing the external tibial plateau (Figs. 4, 5). The differential diagnosis involved a tibial osteomyelitis or a malignant tumoral lesion (chondrosarcoma, bone lymphoma or giant cell tumour). Wide excision and curettage of the bone were performed, by means of a lateral approach, testing the cartilage integrity, and bone defect was filled with cement. Histological examination showed a chronic inflammatory process, with caseous granulomas, microabscesses and Langhans cells. Ziehl-Nielsen and Gram stains were again negative but Löwenstein culture was positive for Mycobacterium tuberculosis. The patient completed treatment with rifampicin, isoniazid, ethambutol and pyrazinamide for 2 months followed by rifampicin and isoniazid for 7 months. One year later, the patient was asymptomatic, and the range of movement of the knee was normal.

Fig. 1
figure 1

Anteroposterior X-ray view of the left knee, showing a normal exploration

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Fig. 2
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Lateral X-ray view of the left knee, also considered normal

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Fig. 3
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Body bone scan scintigraphy (99m Tc-HMDP) shows an area of increased activity on the lateral compartment of the tibial plateau

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Fig. 4
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The MRI of this patient in coronal view showed a low signal intensity focal area on T1-weighted image in the left tibial plateau, extended to disrupted cortical layer and adjacent soft tissues. Some serpiginous foci of high signal intensity were seen on the inner margin of the lesion

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Fig. 5
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MRI in sagittal view on T2-weighted image showed a low signal intensity focal area surrounded by high signal intensity margins in the proximal third of the left tibia and contiguous soft tissues. Moderate amount of joint fluid was seen in the suprapatellar recess

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Discussion

An increased incidence of patients with osteoarticular tuberculosis has been observed due to human immunodeficiency virus infection, immigration from endemic areas, alcoholism, chronic kidney disorders, immunosuppressive therapy, drug addiction, intraarticular steroid injection and systemic illness [11, 16]. Extrapulmonary tuberculosis represents at least 10% of all infections by M. tuberculosis, spinal tuberculosis being the most common form of osteoarticular tuberculosis, followed by hip and knee [7, 12]. Osteoarticular tuberculosis is caused by haematogenous, lymphatic or direct local spread of tubercle bacilli from other lesions from a quiescent pulmonary primary or other extraosseous focus, although direct inoculation has been already reported [2, 14]. Tuberculosis is usually a monoarticular disease, being most of the cases of monoarticular arthritis tuberculous [4, 9, 13]. There are few cases of tuberculous osteitis without joint damage [1, 3, 5, 15]. Knee tuberculosis presents usually as a chronic pain, local tenderness and progressive loss of function that could be intermittent and may delay the diagnosis [8, 10]. In approximately 50% of the patients, no radiographic evidence of pulmonary involvement can be identified and a negative tuberculin skin test does not exclude the diagnosis, as in immunocompromised patients (i.e. patients with chronic renal failure) who had a high rate of anergy. In the early stages, radiological findings are nonspecific. The typical radiographic findings are periarticular osteoporosis, peripherally located osseous erosions and gradual narrowing of the cartilage space, and they appear later on. In order to evaluate soft tissue affection, MRI is the best complementary method. Bone scans with technetium 99m are useful in identifying osteomyelitis foci. To achieve a definitive diagnosis, it is essential to identify M. tuberculosis; however, bone and joint tuberculosis are paucibacillar and many a time Ziehl-Nielsen stain is negative and it becomes necessary to wait for Löwenstein culture. Examination of a biopsy specimen is an important and useful diagnostic method, and a biopsy should be performed in every case of osteoarthritis, in order to know which pathogen is responsible. Probably, amplifying DNA of M. tuberculosis from synovial fluid or bone by polymerase chain reaction could be a useful tool for the early diagnosis of tuberculosis. In conclusion, tuberculosis should be considered in immunosupressed patients with osteoarthritis, particularly if they do not respond to antibiotics. The 9 months of treatment was associated with a good clinical and functional result.

Conflict of interest

No benefits in any form have been received or will be received from any commercial party related directly or indirectly to the subject of this article.