Psoas abscess during treatment with intravenous tocilizumab in a patient with rheumatoid arthritis: a case-based review

Abstract

Interleukin-6 receptor antagonist tocilizumab is a biologic drug used for treating patients with active rheumatoid arthritis (RA) who failed to respond to synthetic or other biologic disease-modifying antirheumatic drugs or where they were contraindicated. Interleukin-6 receptor blockade results in a decrease of disease activity but has some potential adverse effects, the most common being infections. We present a case of a 75-year-old female patient with long-lasting RA, several comorbidities and multiple prior therapies, who developed back pain and general malaise during tocilizumab intravenous treatment. The laboratory findings were typical of toxemia, and the imaging findings revealed large psoas muscle abscess. Surgical and antibiotic treatment was performed with a good outcome. To our knowledge, this has been the first case of a psoas abscess in a patient with RA treated with tocilizumab described in the literature so far. We also present a review of the literature regarding infection, and particularly abscess formation in patients treated with biological disease-modifying antirheumatic drugs, tocilizumab included.

Keywords: Abscess; Arthritis; Diagnosis; Psoas; Rheumatoid; Tocilizumab; Treatment.

Fig. 1

Abdominal ultrasonography: inhomogeneous formation next to the lower pole of the left kidney, partly solid and partly liquid (arrows)

Fig. 2

a Abdominal CT scan—coronal view: a well circumscribed retroperitoneal collection of dense liquid and partially gaseous contents (arrows) measuring 10 × 10 × 17 cm in projection of the left psoas muscle. b Abdominal CT scan—axial view: a collection of dense liquid and partially gaseous contents (arrows) within and along the left psoas muscle

Fig. 3

Control MRI: an abscess collection within the left psoas muscle (arrow), measuring 5 × 7 cm, with surrounding inflammation of adipose tissue