Common low back pain hiding tuberculous sacroiliitis.

The sacroiliac joint is rarely affected by tuberculosis. Only few cases have been reported. Consequently, the diagnosis is often delayed. This case report highlights the importance of continued awareness for early detection and treatment of a tuberculous sacroiliac joint infection.

BACKGROUND

Isolated tuberculosis of the sacrum is rarely reported in the literature, mostly limited to sporadic cases, with a frequency estimated at approximately 0.3%–0.5% for all tuberculosis cases. , Its presenting symptoms are non‐specific, with a predominance of vague back pain.

CASE PRESENTATION

We report the case of a 61‐year‐old healthy female who visited our rheumatology outpatient unit in Mongi Slim hospital in Tunisia on August 2021, complaining about a history of low back pain lasting for 2 years with no radicular irradiation. Her pain increased at efforts and decreased at rest with no night awakeness and no relief under paracetamol. Otherwise, she did not complain about arthralgia, cutaneous eruption, ocular manifestations, or respiratory symptoms. Besides, she did not report constitutional symptoms such as fever, weight loss, asthenia, or anorexia. Her BCG vaccination had been performed during childhood. She reported being in contact with a family member who had lymph node tuberculosis. Physical examination revealed a temperature of 37.5°C. A 3 cm Schober test was conducted, and straight‐leg raise was negative. The range of motion of the hips was normal. Evidence of sacroiliac disease was found, with Patrick‐Fabere’s test positive for the left hip pain and upon pressure on the left iliac wings and over the left sacroiliac joint was painful. We noted a nontender swelling measuring 3x3 cm situated in the right hip region with a normal overlying skin. There was no sensory or motor changes in either lower limbs. Laboratory tests showed inflammation (erythrocyte sedimentation rate, 40 mm/h; C‐reactive protein, 19 mg/l). Blood cell counts were normal. A tuberculin skin test was positive, with an induration of 15 mm.

A plain radiograph of the pelvis showed widening of the left sacroiliac joint space with erosions of the subchondral bone (Figure1). Magnetic resonance imaging confirmed the left sacroiliitis and showed a collection in the left sacroiliac joint and in the left iliopsoas muscle with an extension to the sacral spinal canal (Figures 2 and 3). A fistula was born from an opening inside the sacral spinal canal, along the first sacral nerve root, to an outside opening in the left gluteal area, resulting in an abscess measuring 3.8 × 14.4 cm. Considering these aspects, the most likely diagnosis was tuberculous sacroiliitis. Percutaneous drainage of the abscess was performed. Smears of the aspirated material did not reveal acid‐fast bacilli, the culture on Lowenstein‐Jensen medium was negative, but PCR performed on the specimen was positive for mycobacterium tuberculosis. The patient was started on four‐drug antituberculous therapy including isoniazid, rifampin pyrazinamide, and ethambutol. She experienced significant improvement soon after the initiation of the treatment. Currently after three months of treatment (2 months of intensive phase followed by 5 months of daily isoniazid and rifampicin), she only complains of a minimal discomfort on her back pain with no relapse of the swelling.

FIGURE 1

Plain radiograph of the pelvis showed widening of the left sacroiliac joint space with erosions of the subchondral bone

FIGURE 2

Magnetic resonance imaging (MRI) of the pelvis showing a left sacroiliitis and a collection in the left sacroiliac joint (arrow)

FIGURE 3

MRI image of pelvic and bilateral femur showing extension of the abscess distally around the left greater trochanter

DISCUSSION

Tuberculosis remains endemic in developing countries, where it constitutes a major public health problem. Sacroiliac joint tuberculosis is an uncommon and elusive clinical diagnosis.

CONCLUSION

This pathology should always be suspected in non‐specific chronic low back pain.

CONFLICT OF INTEREST

None.

AUTHOR CONTRIBUTION

Miladi Saoussen made substantial contributions to conception and acquisition of data. Hiba Ben Ayed made substantial contributions to conception, analysis, and interpretation of data. Fazaa Alia was involved in revising the manuscript critically for important intellectual content. Sellami Meriem and Ouenniche Kmar were involved in revising the manuscript critically for important intellectual content. Sellami Meriem, Souabni Leila, Kassab

ETHICAL APPROVAL

Written informed consent was obtained from the patient to publish this report in accordance with the journal’s patient consent policy. Selma, and Chekili Selma gave final approval of the version to be published.

CONSENT

Written informed consent was obtained from the patient to publish this report in accordance with the journal’s patient consent policy.