Fathala Ahmed
Department of Radiology, King Faisal Specialist Hospital & Research Center, MBC#28 P.O. Box 3354, Riyadh, Saudi Arabia.
Radiol Case Rep. 2020 Apr 7;15(6):705-708. doi: 10.1016/j.radcr.2020.03.010. eCollection 2020 Jun.
Cardiac amyloidosis (CA) is an important cause of restrictive cardiomyopathy and heart failure with preserved ejection fraction (HFpEF). At present, 3 bone-seeking tracers, Tc-diphosphono-1,2-propanodicarboxylic acid (Tc-DPD), Tc-pyrophosphate (Tc-PYP), and Tc-hydroxymethylene diphosphonate (Tc-HMDP), have been evaluated for detecting CA, but they are not widely available. In contrast, methylene diphosphate (MDP) is widely available. However, only sporadic case reports have shown that MDP can accumulate in patients with CA. We report an 86-year-old man with multiple medical problems, including hypertension, hyperlipidemia, HFpEF, and a history of treated prostate cancer, who was referred for a Tc-MDP bone scan to rule out bone metastasis. The bone scan was negative for bone metastasis, but there was mild tracer accumulation in the heart, suggestive of CA. Subsequently, CA was diagnosed on Tc-PYP imaging. MDP may play a role comparable to other bone-seeking tracers in the diagnosis of CA and may be used as a noninvasive adjunct in the diagnosis of CA. Future research should compare MDP with other bone-seeking tracers for the diagnosis of CA. In addition, mechanistic studies on tracer binding to amyloid fibrils may help understand the pathophysiology of CA and facilitate the development of better and more specific tracers for CA.
心脏淀粉样变性（CA）是限制性心肌病和射血分数保留的心力衰竭（HFpEF）的重要病因。目前，已对3种亲骨性示踪剂，即锝二膦酸-1,2-丙二羧酸（Tc-DPD）、锝焦磷酸盐（Tc-PYP）和锝羟亚甲基二膦酸盐（Tc-HMDP）进行了检测CA的评估，但它们并未广泛应用。相比之下，亚甲基二膦酸盐（MDP）应用广泛。然而，仅有零星的病例报告显示MDP可在CA患者体内蓄积。我们报告了一名86岁男性，患有多种疾病，包括高血压、高脂血症、HFpEF以及前列腺癌治疗史，因行Tc-MDP骨扫描以排除骨转移而前来就诊。骨扫描结果显示无骨转移，但心脏有轻度示踪剂蓄积，提示可能患有CA。随后，经Tc-PYP显像确诊为CA。MDP在CA诊断中可能发挥与其他亲骨性示踪剂类似的作用，可作为CA诊断的一种无创辅助手段。未来的研究应比较MDP与其他亲骨性示踪剂在CA诊断中的效果。此外，关于示踪剂与淀粉样纤维结合的机制研究可能有助于理解CA的病理生理学，并促进开发更好、更具特异性的CA示踪剂。
