一名70多岁男性患者出现肩膀和盆腔部位僵硬和疼痛的症状。他的C反应蛋白水平升高至116 mg/L，初步诊断为多发性肌炎。20 mg/天的泼尼松治疗仅仅带来了有限的改善，尽管同时使用了免疫抑制剂，但病情仍然反复发作。广泛的调查未能揭示潜在的病因。五年后，出现了明显无痛性血尿，发现了浸润性乳头状尿路上皮癌。对分期CT扫描的复查发现，与他初始表现相比，双侧侵蚀性骶髂关节炎的表现已经发展。根治性膀胱前列腺切除手术暂时缓解了症状，但在又过了9个月后，病情复发，并发现转移扩散。富含肿瘤的骶髂关节炎是一种罕见的临床实体；据我们所知，这是首次报道与实体肿瘤相关的病例。© BMJ Publishing Group Limited 2023. 不得商业再利用。请查看权利和权限。BMJ出版。

A man in his early 70s presented with stiffness and aching in the shoulder and pelvic girdles. His C reactive protein level was elevated at 116 mg/L, leading to an initial diagnosis of polymyalgia rheumatica. Treatment with prednisone at 20 mg/day provided limited improvement and relapses recurred despite concomitant immunosuppressive agents. Extensive investigations failed to reveal an underlying aetiology.Five years later, gross painless haematuria led to the detection of an invasive papillary urothelial carcinoma. A review of the staging CT scan revealed findings compatible with bilateral erosive sacroiliitis, which had developed since his initial presentation. Radical cystoprostatectomy provided temporary relief but after a further 9 months, symptoms relapsed, and metastatic spread was discovered.Paraneoplastic sacroiliitis is a rare clinical entity; and to the best of our knowledge, this is the first reported case associated with a solid tumour.© BMJ Publishing Group Limited 2023. No commercial re-use. See rights and permissions. Published by BMJ.