全身骨骼掃描之顱骨異常攝取探討──案例報告

Abnormal Radiotracer Uptake in the Skull on Whole-Body bone scan: A case Report

全身骨骼掃描是核醫科應用非常廣泛的檢查項目之一。Tc-99mMDP與成骨細胞活性成比例，因此骨骼修復較多的部位就會吸收較多的磷酸鹽，而在全身骨骼掃描上呈現放射性攝取增高的影像。臨床上造成攝取增高的原因，包含骨折、感染、骨轉移和不太常見的骨病等。一名68歲女性，有乳癌與末期腎臟疾病（End Stage Renal Disease, ESRD）病史。於2021年4月進行核醫全身骨骼掃描（Tc-99mMDP），影像呈現整個顱骨、面部骨骼和整個下頜骨有瀰漫性放射性攝取增高。本案例為ESRD患者，疑似為尿毒症獅面臉（Uremic Leontiasis Ossea, ULO）。由於ESRD患者繼發性的副甲狀腺功能亢進導致顱骨過度生長，表現方式為下頜骨和上頜骨擴大以及其他顱骨變形等。尿毒症獅面臉是一種慢性疾病，在慢性腎病、繼發性的副甲狀腺功能亢進和腎性骨營養不良患者中普遍存在。因此，當全身骨骼掃描呈現顱骨異常攝取時，需考慮是因ESRD及腎性骨營養不良而引起的。

Whole-body bone scan (WBBS) is widely applied in nuclear medicine, and technetium 99m-methyl diphosphonate (Tc-99m MDP) uptake is proportional to osteoblastic activity. Therefore, areas with higher bone repair activity absorb a greater amount of phosphate, which manifests as increased radiotracer uptake on WBBS. In clinical practice, causes of increased uptake include fractures, infections, bone metastases, and less commonly, bone diseases. A 68-year-old woman with a history of breast cancer and end-stage renal disease (ESRD) underwent Tc-99m MDP WBBS in April 2021. WBBS revealed increased diffuse radiotracer uptake in the entire skull, facial skeleton, and mandible. Clinically, enlargement of the mandible and maxilla and deformation of other cranial bones was observed; the excessive growth of the cranial bones was attributed to secondary hyperparathyroidism caused by ESRD. Considering that the patient had ESRD, uremic leontiasis ossea (ULO) was suspected. ULO is a chronic condition commonly found in patients with chronic renal disease, secondary hyperparathyroidism, and renal osteodystrophy. Therefore, in patients with abnormal skull uptake on WBBS, the possibility of ESRD-associated renal osteodystrophy should be considered.