INTRODUCTION

Tuberculosis (TB) of the bone is a disease that was diagnosed 9000 years ago in the Egyptian mummies.¹ It is estimated to be 10–35% of extrapulmonary TB cases in most studies.² The most common type of skeletal TB is known to be spinal TB, which is known as Pott’s disease. This type of skeletal TB compromises around half of the musculoskeletal TB cases, followed by arthritis and extraspinal osteomyelitis.³

After infection with Mycobacterium tuberculosis (MTB), the organism seeds in the bone or the synovial tissue, where the infection at that time is contained by local immune reaction with no or non-significant subclinical manifestation of the disease. Once the immunity fails, as in the case of Human immunodeficiency virus (HIV), renal or liver impairment, malnourishment or aging, and reactivation of the infection occurs, though in reported cases reactivation of TB might occur without any clear associated comorbidities. Two distinctive types of bone and joint infections occur with TB; a caseous pattern, which is generally more common in children and is characterized by bone destruction, abscess formation, and development of sinus. The other type is granular, which is more common in adults and has an insidious pattern with less aggressive and destructive form in comparison to the caseous form. However, typically, patients display overlap of both types of infections.⁴

Here, we present a case of a Pilipino female without comorbid illness, who was diagnosed to have tuberculous osteomyelitis with extensive involvement of lumbosacral vertebrae and surrounding soft tissue and muscles with multiple retroperitoneal collections. She responded dramatically to antituberculosis therapy.

Case presentation

A 29-year-old Pilipino female working as a food handler in one of the fast-food restaurants in Bahrain presented to Salmaniya Medical Complex with complaint of lower back pain of three months duration. The patient noticed that the severity of the pain was increasing in a gradual pattern with less response to analgesia. Few days before presenting to medical attention, she noticed a discharging sinus in the lower lateral left side of her back; the discharge was yellowish and copious. History of fever, night sweats, weight loss, lower limb weakness, respiratory symptoms, familial or personal history of TB, or contact with positive cases were not noticed.

On evaluation, the patient was thin-built, conscious with significant muscle rigidity of her back leading to difficulty and reluctancy to move in the bed. On focused examination of her back, she had a draining sinus on the lateral left side of her lower back, which was a continuously pouring, thick, yellowish creamy discharge. Bending, turning, and lateral movements of the back were limited to the lumbar region with local tenderness. The respiratory, cardiovascular, and abdominal examinations were normal. On central nervous system examination, the power of all the limbs was normal and her reflexes and sensations were intact. Based on examination of the vitals, tachycardia and low-grade fever were detected.

The initial laboratory investigations showed normal full blood count, normal liver and renal function tests, raised estimated sedimentation rate (ESR) at 66 mm/hour, and C-Reactive Protein (CRP) at 14.5 mg/L; however, HIV serology was negative. Plain x-ray of the lumbosacral (L) spine revealed significant destruction and sclerosis of L5 vertebra with associated reduction of the L4-L5 disc height. Sclerosis with erosion of the anterior aspect of the sacrum was noticed (Figure 1). The sacroiliac joint was spared, and the patient was admitted for further evaluation and treatment.

A contrast-enhanced computed tomography (CECT) scan of the abdomen and pelvis was performed, which showed destructive changes of the L5 vertebra with multifocal abscesses involving bilateral psoas muscles, left iliacus muscle, and left gluteal muscle with multi-loculated abscess extending to the subligamentous area anterior to the vertebral body. The collection contained multiple gas pockets (Figure 2 a and b).

Destructive changes involving the L5 vertebra (blue circle), bilateral psoas muscle multi focal abscesses (red asterisk), multi-loculated abscess extending to the subligamentous area anterior to the vertebral body (blue arrows), subiliac muscle abscess on the left side (yellow asterisk), left gluteal intramuscular abscess—note the gas pocket within the collection indicating infection (yellow arrows).

This was further clarified in the sagittal reformat in the soft tissue window (Figure 2 c), which showed destruction and reduction of L5 height (< 50%) along with sclerosis of the S1 vertebra; however, the remaining levels were normal. Associated reduction in L4-L5 and to a lesser extent in L5-S1 intervertebral disc space was observed. The fragmented L5 bone was projecting posteriorly resulting in severe narrowing of the central canal.

Multi-loculated retroperitoneal collection centered on L5-S1 extended superiorly involving the psoas muscles bilaterally and extending up to the level of L2. The collection extended inferiorly to the level of S2-S3. On the left side, the collection extended within the subligamentous area anterior to the bodies of L5 below to the sacrum. The collection, anterior to the sacrum, measured 854.5 cm and the left side collection measured 11.58.52 cm at their maximum dimensions. The hip joint and visualized levels of the femur bones were normal. The radiological impression was spondylodiscitis favoring tuberculosis as the primary cause.

A sample from the discharging sinus was sent for microbiological analysis and the result disclosed positive MTB by real-time polymerase chain reaction (RT-PCR) using GeneXPert (Cepheid, United States) without genetic detection of rifampicin resistance.

In view of clinical, radiological, and laboratory results, the patient was diagnosed for tuberculous osteomyelitis of the vertebral spine complicated by epidural collection, psoas abscess, and extensive involvement of the surrounding soft tissue and muscular structures. Accordingly, first-line quadruple antituberculosis therapy (rifampicin 450 mg, isoniazid 300 mg, pyrazinamide 1000 mg, ethambutol 800 mg, and vitamin b6 one tablet per day) was initiated. During the patient’s stay in the hospital for two weeks, the pain reduced gradually, movements and mobilization improved due to less pain, and discharge from the sinus reduced and completely stopped by the second week, after initiation of the antituberculosis therapy. The patient was discharged home after two weeks and was walking normally without assistance or pain. The culture was traced, and it grew MTB with full sensitivity to all first-line treatment drugs (rifampicin, isoniazid, pyrazinamide, ethambutol).

Figure 1: Frontal radiograph of the lumbosacral spineshowing: destruction and sclerosis of the L5 vertebra with associated loss ofvertebral body height (yellow arrow), reduction in L4-L5 disc height (bluearrow), and erosion and sclerosis of the sacrum (black arrow)

Figure 2.a: A contrast- enhanced computed tomography (CECT) scan of the abdomen and pelvis

Figure 2.b: A contrast- enhanced computed tomography (CECT) scan of the abdomen and pelvis

Figure 2.c: Sagittal reformat from a contrast-enhanced computedtomography (CECT) scan in the soft tissue window showing multi-loculatedabscess extending within the subligamentous area anterior to the bodies of L5 belowto the sacrum (red arrows), destruction of the L5 vertebra with reduction of theL5 vertebral body height, sclerosis of the S1 vertebra and reduction in L4-L5and to a lesser extent L5-S1 intervertebral disc space (blue circle), and thefragmented L5 bone projecting posteriorly resulting in severe narrowing of thecentral canal measuring about 0.4 cm in the anterior-posterior dimension(blue arrow)

DISCUSSION

The bone involvement in TB is a result of either primary seeding or contiguous spread from adjacent foci.⁵ Spinal TB is the most common type of skeletal TB, and typically involves lower thoracic and upper lumbar vertebrae; less commonly it involves other regions. In our case, the disease involved the lower lumbar (L4, L5) and upper sacral (S1) vertebrae. A rare case of cervical spine TB was reported in 2010 in a 48-year-old Vietnamese woman, who presented with compression fracture of the cervical spine (C7) following months of neck pain and upper limb numbness. It was initially interpreted as metastasis rather than TB until a tissue biopsy confirmed the infectious origin of her symptoms.⁶

Spinal TB in its classical presentation involves the vertebral body with its intervertebral disc (spondylodiscitis) and generally involves more than one adjacent vertebral bodies due to the nature of the arterial supply of the vertebral segments, which bifurcate to supply two adjacent vertebrae.^7,8 These features are consistent in our case, wherein involvement of the three contiguous vertebrae (L4, L5, and S1) and the L4-L5 and L5-S1 intervertebral disc spaces were observed. The most common symptoms of spinal osteomyelitis are chronic back pain along with muscle spasm and rigidity, whereas, constitutional symptoms of fever, weight loss, and sweating are seen in < 40% patients.⁹ In our case, the presentation was mainly localized symptoms of back pain with muscle spasm and rigidity, however constitutional symptoms were absent.

Some patients may present with neurological symptoms once the intervertebral disc is involved and gradual destruction occurs. In our case, neurological symptoms or signs were not observed, despite involvement and reduction of L4-L5 and L5-S1 intervertebral disc spaces with associated narrowing of the central canal.

Imaging techniques have an essential and crucial role in the diagnosis of spinal tuberculosis. Computed tomography (CT) studies are cost effective in clinical practice.¹⁰ However, magnetic resonance imaging is the most accurate imaging technique to identify bone destruction, granulomatous tissue, and tuberculomas, which may not be clearly visible on plain x-rays and/or CT imaging. However, obtaining microbiological samples through aspiration or needle biopsy is always mandated to confirm the diagnosis and to check the drug susceptibility.¹¹ In our case the extensive destructive lesions seen on CT images in combination with the acid-fast Bacilli stain of the sinus discharge were sufficient to reach a definitive diagnosis without the need for tissue sample. Another case reported in 2016, involved a 22-year-old female Chinese farmer, who was diagnosed with extensive spinal TB extending to the sacroiliac joints in addition to other body organs. The initial diagnosis was through imaging and she was commenced on antituberculosis regimens based on CT scan results. After surgery a confirmatory tissue biopsy was obtained.¹²

The worst complications of spinal tuberculosis are neurological weakness, such as paraplegia or quadriplegia with an incidence of 10–43%.13 It was reported that patients with atypical TB presentation on imaging, such as skip lesions are more susceptible for spinal cord compression with neurological complications due to the late diagnosis and delay in initiating appropriate medical therapy.¹⁴

The appropriate treatment modality of spinal osteomyelitis is mainly dependent on the presence of associated neurologic deficits. Medical treatment with quadruple therapy is the mainstay of treatment. In cases with neurologic deficits, surgical intervention is generally indicated in addition to the medical therapy.¹⁵ The duration of therapy for the treatment of musculoskeletal TB is not well defined. For majority of the patients receiving first-line agents, nine months of therapy is essential.¹⁶ Among patients with extensive disease and those who did not receive the first-line agents, a longer duration (12 months) might be required. Our patient was started on first-line quadruple therapy (rifampicin, isoniazid, pyrazinamide, and ethambutol) as the isolate was completely sensitive to all first-line drugs. The plan was to continue with the initial phase for two months then to switch to the continuation phase (rifampicin and isoniazid) for further seven months for a total of nine months of therapy.

CONCLUSION

Nowadays, spinal tuberculous osteomyelitis is not common in Bahrain. It is challenging to diagnose due to the unfamiliarity of the practitioners in Bahrain with the disease, low TB burden in the country, and its insidious presentation of back pain, which can be misdiagnosed. Our case report shows extensive form of the disease, which was complicated by discharging sinus with extraspinal involvement. It emphasizes the importance of practitioners to consider TB as one of the differential diagnoses among patients presenting with chronic back pain; particularly among expatriates from high TB burden countries, even in the absence of any pulmonary involvement. Early diagnosis and rapid initiation of medical treatment aids in preventing a lot of devastating illnesses and functional deficits.