In this case report, we describe an uncommon case of neuroendocrine cancer of unknown origin began with cauda equina syndrome in a patient affected by Paget disease of bone (PDB). A 76-year-old man with diagnosis of PDB, without history of pain or bone deformity, developed sudden severe low back pain. Bone alkaline phosphatase was increased and MRI and whole-body scintigraphy confirmed the localization of the disease at the third vertebra of the lumbar spine. Treatment with Neridronic Acid was started, but after only 2 weeks of therapy anuria and bowel occlusion occurred together with lower limb weakness and walking impairment. Cauda equina syndrome consequent to spinal stenosis at the level of L2–L3 was diagnosed after admission to Emergency Department and the patient underwent neurosurgery for spinal medulla decompression. The histologic results showed a complete subversion of bone structure in neoplastic tissue, consistent with metastatic neuroendocrine carcinoma of unknown origin. In conclusion, low back pain in the elderly may require deep investigation to individuate rare diseases. In asymptomatic patients with apparently stable PDB, the sudden appearance of pain or neurologic symptoms may alert the clinician for the possibility of other superimposing diseases, like bone metastases.

在本病例报告中，我们描述了一个罕见的不明原因神经内分泌癌病例，该病例始于一名佩吉特骨病 (PDB) 患者的马尾综合征。一名被诊断为 PDB 的 76 岁男性，没有疼痛或骨骼畸形史，突然出现严重腰痛。骨碱性磷酸酶升高，MRI 和全身闪烁扫描证实疾病定位在腰椎第三椎骨。开始使用奈立膦酸治疗，但仅治疗两周后就出现无尿和肠闭塞，同时下肢无力和行走障碍。入院急诊后诊断为 L2-L3 椎管狭窄所致的马尾综合征，并接受神经外科脊髓减压术。组织学结果显示肿瘤组织中骨结构完全颠覆，与来源不明的转移性神经内分泌癌一致。总之，老年人腰痛可能需要深入研究以个体化罕见疾病。在表面稳定的 PDB 的无症状患者中，突然出现的疼痛或神经系统症状可能会提醒临床医生其他叠加疾病的可能性，例如骨转移。