Hawkins P N
Royal Postgraduate Medical School, Hammersmith Hospital, London, UK.
Baillieres Clin Rheumatol. 1994 Aug;8(3):635-59. doi: 10.1016/s0950-3579(05)80120-7.
The diagnosis of systemic amyloidosis is only occasionally suspected on clinical grounds alone and is more often considered when an associated condition, such as a chronic inflammatory disease or monoclonal gammopathy, is present. No blood test is diagnostic of amyloid although routine haematological and biochemical investigations have important roles in defining the underlying disease process in amyloidosis, and evaluating organ function. A number of non-invasive investigations including echocardiography, electrocardiography and soft tissue scintigraphy with bone-seeking tracers give characteristic results in some patients with amyloidosis, but are non-specific. The diagnosis can only be confirmed by demonstrating the presence of amyloid deposits in the tissues. Histology is the traditional method in routine clinical practice and is sensitive for revealing microscopic deposits and permits immunotyping of fibril proteins. Disadvantages are that biopsies are invasive, open to sampling error and can only give limited information on the distribution and extent of amyloid deposits in an individual. Scintigraphic and turnover studies with radioiodinated SAP are new specific methods for confirming the presence of amyloid in tissues, based on the affinity of SAP for all types of amyloid fibril. Labelled SAP scans survey the whole body macroscopically for the presence and anatomical distribution of amyloid in a quantitative manner, and SAP turnover studies provide information on the whole body amyloid load. Although the availability of SAP scintigraphy presently remains restricted, the technique has been used in over 400 patients with amyloid in prospective studies, and has already provided a number of new insights into the natural history of amyloidosis. These include the observation that there is a consistently poor correlation between the quantity of amyloid in an organ and the resulting degree of functional impairment. Amyloid deposits accumulate at rates which vary substantially between different organs in a single subject and between individuals with similar types of amyloidosis, even when the rates of amyloid fibril precursor protein supply are apparently similar. In some patients amyloid accumulation may plateau without any measurable alteration in the precursor supply. In patients with amyloidosis in whom the supply of fibril precursors is reduced, either as a result of therapy directed towards the underlying process or through a natural remission, substantial regression of amyloid frequently occurs. This has been observed in patients with AA, AL and variant TTR-associated amyloidosis, and is usually associated with clinical benefits. In some such cases, however, the function of affected organs may continue to deteriorate despite halting the accumulation of amyloid, presumably because irreversible structural damage has already occurred.(ABSTRACT TRUNCATED AT 400 WORDS)
系统性淀粉样变性仅偶尔仅凭临床依据被怀疑，更多时候是在存在诸如慢性炎症性疾病或单克隆丙种球蛋白病等相关病症时才被考虑。虽然常规血液学和生化检查在确定淀粉样变性的潜在疾病过程以及评估器官功能方面具有重要作用，但没有一项血液检查能确诊淀粉样变性。包括超声心动图、心电图以及使用亲骨性示踪剂的软组织闪烁扫描在内的一些非侵入性检查，在一些淀粉样变性患者中可得出特征性结果，但均不具有特异性。只有通过证明组织中存在淀粉样沉积物才能确诊。组织学是常规临床实践中的传统方法，对于揭示微观沉积物很敏感，并能对纤维蛋白进行免疫分型。缺点是活检具有侵入性，存在抽样误差，且只能提供关于个体淀粉样沉积物分布和范围的有限信息。基于血清淀粉样蛋白P成分（SAP）对所有类型淀粉样纤维的亲和力，使用放射性碘标记的SAP进行闪烁扫描和周转率研究是确认组织中淀粉样蛋白存在的新的特异性方法。标记的SAP扫描以定量方式宏观地检查全身淀粉样蛋白的存在情况和解剖分布，而SAP周转率研究提供有关全身淀粉样蛋白负荷的信息。尽管目前SAP闪烁扫描的可用性仍然有限，但该技术已在前瞻性研究中应用于400多名淀粉样变性患者，并已经为淀粉样变性的自然史提供了一些新见解。这些见解包括观察到器官中淀粉样蛋白的数量与由此产生的功能损害程度之间始终存在较差的相关性。在单个受试者的不同器官之间以及患有相似类型淀粉样变性的个体之间，淀粉样沉积物的积累速率差异很大，即使淀粉样纤维前体蛋白的供应速率明显相似。在一些患者中，淀粉样蛋白的积累可能会达到平稳状态，而前体供应没有任何可测量的变化。在因针对潜在疾病过程的治疗或自然缓解而导致纤维前体供应减少的淀粉样变性患者中，淀粉样蛋白经常会大量消退。这在AA型、AL型和变异型转甲状腺素蛋白相关淀粉样变性患者中均有观察到，并且通常伴有临床益处。然而，在一些此类情况下，尽管淀粉样蛋白的积累停止，但受影响器官的功能可能会继续恶化，推测是因为已经发生了不可逆的结构损伤。（摘要截选至400字）
