Inflammatory Back Pain and Psoriasis: Expecting Spondyloarthritis, Discovering Lymphoma.

Inflammatory back pain is a characteristic of spondyloarthritis. It is not, however, an exclusive symptom of inflammatory rheumatic diseases as it can also be associated with non-inflammatory entities. Infrequently, the etiology can be found in neoplastic conditions such as malignant lymphoma. Even in the presence of comorbidities indicatory of underlying rheumatic disease, like psoriasis vulgaris, the clinician should not be led astray. It is essential to pay attention to contradictory findings, as treatment crucially differs depending on diagnosis. Herein, we report on a psoriasis patient who presented with characteristic inflammatory back pain and deceptive imaging results. While the patient was initially thought to suffer from an inflammatory rheumatic disease with axial involvement, it was the accompanying atypical circumstances, particularly her age, that instantly challenged the diagnosis of axial psoriatic arthritis. She was eventually diagnosed with stage IV follicular lymphoma that manifested with rare and exclusively extranodal lesions and spondyloarthritis-like morphology. This case effectively demonstrates the importance of a thorough diagnostic workup and how certain clinical factors, such as the patient's age, should be considered when confronted with inflammatory back pain.