Teaching Case

A 65-year-old man who was referred to our hospital for an evaluation of high metabolic activity in 18Fluorodeoxyglucose-PET- in the area of the gluteus maximus muscle (SUV max 10.6).

Patient with primary MALT lymphoma (mucosa-associated lymphoid tissue lymphoma) of the left kidney treated with 8 cycles of chemotherapy (RCVP – rituximab, cyclophosphamide, vincristine, prednisolone) with good response.

Laboratory tests: Autoimmune haemolytic anaemia.

Symptoms: Persistent low back pain.

MRI (magnetic resonance imaging) of the sacroiliac joint (3T scanner) was performed using T2-weighted, T1-weighted, STIR, diffusion-weighted imaging, and fat-saturated contrast-enhanced T1-weighted sequences.

Figure 1.  Transverse T2-weighted magnetic resonance image showing increased T2 signal intensity over the left sacroiliac joint and the left gluteus maximus muscle. Irregular fluid collection (hyperintense in T2) was noted posterior to the left sacroiliac joint.

Figure 2. T1-weighted magnetic resonance image showing decreased T1 signal intensity over the left sacroiliac joint.

Figure 3. T1-weighted with fat saturation and gadolinium-enhanced image show the bone marrow oedema in left sacroiliac joint, overlying soft tissue swelling, left gluteal muscles abscess and multilocular abscess involving the left sacroiliac joint.

Figure 4. Sagittal gadolinium-enhanced T1-weighted with fat saturation image shows a rim enhancement area indicating an abscess and bone-marrow oedema.

Figure 5. Diffusion-weighted imaging clearly demonstrates the extension of the abscesses.

 MRI examination shows: left sacroiliitis and osteomyelitis; with extensive abscess formation spreading dorsally to the gluteal region; left sacroiliac joint space was enlarged; the joint margins revealed significant destruction and irregularity. 

Background: Skeletal tuberculosis comprises approximately 3–5% of all tuberculoses. The sacroiliac joint is involved in 3–9%. Isolated sacroiliac involvement is very rare. [1, 2]

Clinical Perspective: It usually presents as vague back pain. Tuberculous sacroiliitis is frequently missed because of their vague and non-specific clinical presentation. [1, 3]

Imaging Perspective: Radiographs and ultrasound are usually negative during the early course of the disease. The bone scan is helpful for patients with suspected skeletal infection and poorly localising symptoms. MRI is very helpful in the early diagnosis of the disease. [2, 3]

Magnetic resonance imaging (MRI) is the most sensitive modality for diagnosing sacroiliitis. MRI can evaluate cartilage integrity, ligaments, and detect osseous oedema and erosion. STIR images are sensitive for demonstrating bone oedema adjacent to the infected joint. Axial T2-weighted scans demonstrate small joint effusions and adjacent muscle inflammation as a high-signal area. Use of intravenous Gd-DTPA contrast enables the identification or exclusion of an abscess. Definitive diagnosis is obtained by fine needle aspiration or open biopsy. A diagnostic aspiration or closed needle biopsy of the sacroiliac joint is appropriate when the disease is in its early stages with minimal joint destruction. An open biopsy is essential when the aspirate yields no growth. Open debridement should be done in those not responding to conservative management and when an abscess is observed. [1, 2, 3, 4]

Outcome: Most of the patients can be cured with first-line antitubercular drugs, but few might develop multidrug resistance and require second-line drugs. The recommended treatment duration of extrapulmonary tuberculosis is 6–9 months. Operative intervention is required when the patient is not responding to an adequate trial of chemotherapy. [1, 3]

Teaching Points: Early detection of the disease and treatment are key factors in the successful management of the disease. If osteoarticular tuberculosis is diagnosed and treated at an early stage, the large majority of patients are expected to achieve healing with near-normal function. [1, 3, 5)

Written informed patient consent for publication has been obtained.