Inflammatory Back Pain in Malignancy Mimics Spondyloarthritis

Inflammatory back pain (IBP) is a key clinical feature that can help diagnose axial spondyloarthritis (AxSpA). Importantly, IBP can also be caused by infections, drugs (such as isotretinoin), and various malignancies. Commonly known infections that may mimic IBP include Brucella and tuberculosis infection. Hematologic malignancies and solid tumors can also cause IBP through paraneoplastic mechanisms or via metastasis. Thus, a recent study by Albayrak et al sought to present characteristics of patients presenting with IBP in the past 10 years with a final diagnosis of malignancy.

This retrospective, multicenter study was performed in Turkey at multiple tertiary care rheumatology centers. They enrolled patients who presented with IBP in the previous 10 years who were ultimately diagnosed with malignancy as the final diagnosis. Thirty six patients with AxSpA, with similar age/sex ratio of 1:1 from each center, were included as the control group.IBP was defined according to Calin criteria. They collected demographic data as well as disease activity measures (Bath ankylosing spondylitis disease activity index or BASDAI) and laboratory testing (ESR, CRP, CBC, LDH, calcium). All patients had pelvic and lumbar radiographs, with sacroiliac MRI obtained in necessary cases.

Ultimately, 34 patients were included in the malignancy group (mean age 42.6) compared to 36 patients in the control group (mean age 43.6). There were statistically significant differences in the time interval between IBP and diagnosis (21 months in the control vs 4 months in the malignancy group) and in the BASDAI scores (6.1 in malignancy group vs 5.1 in the control group). Of the malignancy group, there were 16 hematologic malignancies (multiple myeloma, acute leukemia, lymphoma) and 18 solid tumors (including breast, lung cancer, bone tumors, prostate, colon). Pain due to metastasis was seen in 27 of the malignancies, and 7 cases of IBP were due to a paraneoplastic condition. Compared to the control group, patients with IBP due to malignancy had higher inflammatory markers (ESR, CRP), higher LDH values, and lower hemoglobin levels.

The authors believe this is the largest case series of IBP with a final diagnosis of malignancy in the literature. They note some unique features of malignancy-related IBP include short interval between symptom onset and diagnosis, with much higher acute phase reactants and LDH levels, and lower hemoglobin values compared to AxSpA.Imaging can also help differentiate AxSpA from malignancy: IBP due to malignancy is often associated with lytic lesions, collapse fractures and infiltrations, compared to bone marrow edema or new bone formation in AxSpA.The authors did not have HLA B27 results in the malignancy cases, which may be a risk factor for IBP in malignancy. Rheumatologists should consider mimics of inflammatory axial spondyloarthritis when evaluating patients with inflammatory back pain.

References:

Albayrak F, Kısacık B, Gündüz İ et al. Inflammatory low back pain-associated malignancies mimicking spondylarthritis. Clinical Rheumatology, September 2024.