Amyloid diagnosis, subcutaneous adipose tissue, immunohistochemistry and mass spectrometry

Early Detection of Multiorgan Light-Chain Amyloidosis by Whole-Body 18F-Florbetapir PET/CT

Immunoglobulin light-chain (AL) amyloidosis affects multiple systemic organs. However, determination of the precise extent of organ involvement remains challenging. Targeted amyloid imaging with ¹⁸F-florbetapir PET/CT offers the potential to detect AL deposits in multiple organs. The primary aim of this study was to determine the distribution and frequency of AL deposits in the various organs of subjects with systemic AL amyloidosis using ¹⁸F-florbetapir PET/CT. Methods: This prospective study included 40 subjects with biopsy-proven AL amyloidosis including active AL amyloidosis (n = 30) or AL amyloidosis in hematologic remission for more than 1 y (n = 10). All subjects underwent ¹⁸F-florbetapir PET/CT, skull base to below the kidney scan field, from 60 to 90 min after injection of radiotracer. Volume-of-interest measurements of SUV_max were obtained using Hermes software for the parotid gland, tongue, thyroid, lung, gastric wall, pancreas, spleen, kidney, muscle, abdominal fat, lower thoracic spine, vertebral body, and humeral head. Uptake in each organ was visually compared with that in spine bone marrow. An SUV_max of at least 2.5 was considered abnormal in all organs other than the liver. Results: Compared with the international consensus definition of organ involvement, ¹⁸F-florbetapir PET/CT identified amyloid deposits in substantially higher percentages of subjects for several organ systems, including parotid gland (50% vs. 3%), tongue (53% vs. 10%), and lung (35% vs. 10%). In several organ systems, including kidney (13% vs. 28%) and abdominal wall fat (10% vs. 13%), PET identified involvement in fewer subjects than did international consensus. Quantitative analysis of ¹⁸F-florbetapir PET/CT revealed more frequent organ involvement than did visual analysis in the tongue, thyroid, lung, pancreas, kidney, muscle, and humeral head. Extensive organ amyloid deposits were observed in active AL as well as in AL remission cohorts, and in both cardiac and noncardiac AL cohorts. Conclusion: ¹⁸F-florbetapir PET/CT detected widespread organ amyloid deposition in subjects with both active AL and AL hematologic remission. In most instances, amyloid deposits in the various organs were not associated with clinical symptoms and, thus, were unrecognized. Early recognition of systemic organ involvement may help tailor treatment, and noninvasive monitoring of organ-level disease may guide management with novel fibril-resorbing therapies.

Kidney Involvement in Systemic Calcitonin Amyloidosis Associated With Medullary Thyroid Carcinoma

A 52-year-old woman with widely disseminated medullary thyroid carcinoma developed nephrotic syndrome and slowly decreasing kidney function. A kidney biopsy was performed to differentiate between malignancy-associated membranous glomerulopathy and tyrosine kinase inhibitor-induced focal segmental glomerulosclerosis. Surprisingly, the biopsy specimen revealed diffuse glomerular deposition of amyloid that was proved to be derived from the calcitonin hormone (Acal), produced by the medullary thyroid carcinoma. This amyloid was also present in an abdominal fat pad biopsy. Although local ACal deposition is a characteristic feature of medullary thyroid carcinoma, the systemic amyloidosis involving the kidney that is presented in this case report has not to our knowledge been described previously and may be the result of long-term high plasma calcitonin levels. Our case illustrates that systemic calcitonin amyloidosis should be considered in the differential diagnosis of proteinuria in patients with medullary thyroid carcinoma.

Amyloidosis: Insights from Proteomics

Amyloidoses are a spectrum of disorders caused by abnormal folding and extracellular deposition of proteins. The deposits lead to tissue damage and organ dysfunction, particularly in the heart, kidneys, and nerves. There are at least 30 different proteins that can cause amyloidosis. The clinical management depends entirely on the type of protein deposited, and thus on the underlying pathogenesis, and often requires high-risk therapeutic intervention. Application of mass spectrometry-based proteomic technologies for analysis of amyloid plaques has transformed the way amyloidosis is diagnosed and classified. Proteomic assays have been extensively used for clinical management of patients with amyloidosis, providing unprecedented diagnostic and biological information. They have shed light on the pathogenesis of different amyloid types and have led to identification of numerous new amyloid types, including ALECT2 amyloidosis, which is now recognized as one of the most common causes of systemic amyloidosis in North America.

Three cases of systemic amyloidosis successfully diagnosed by subcutaneous fat tissue biopsy of the hip

Fine-needle aspiration biopsy of the abdominal fat pad is considered to be a minimally invasive procedure for diagnosing systemic amyloidosis. However, this procedure is sometimes difficult and can be dangerous for elderly patients whose abdominal fat layer is thin because of malnutrition. In such cases, alternative diagnostic methods are required. We report three elderly patients with heart failure complicated by malnutrition. In all cases, electrocardiogram showed low voltage in the limb leads and a pseudoinfarct pattern in the chest leads, and echocardiography showed left ventricular wall thickening with granular sparkling appearance. These patients were suspected of having amyloid cardiomyopathy but could not undergo myocardial biopsies because of their poor conditions. After failed attempts at biopsy of the abdominal fat pad or the other organs, subcutaneous fat tissue biopsy over the hip led to the diagnosis of systemic amyloidosis with cardiomyopathy. The resultant diagnosis guided us to choose the appropriate treatment for the patients. This article illustrates that subcutaneous fat tissue biopsy of the hip could be a useful procedure for diagnosing systemic amyloidosis in elderly patients, particularly when a fat tissue biopsy of the abdomen is associated with a high risk of complications because of malnutrition.

Biochemical markers in early diagnosis and management of systemic amyloidoses

Systemic amyloid diseases are characterized by widespread protein deposition as amyloid fibrils. Precise diagnostic framing is the prerequisite for a correct management of patients. This complex process is achieved through a series of steps, which include detection of the tissue amyloid deposits, identification of the amyloid type, demonstration of the amyloidogenic precursor, and evaluation of organ dysfunction/damage. Laboratory medicine plays a central role in the diagnosis and management of systemic amyloidoses, through the quantification of the amyloidogenic precursor and evaluation of end-organ damage using biomarkers.

A practical approach to the diagnosis of systemic amyloidoses

Accurate diagnosis of systemic amyloidosis is necessary both for assessing the prognosis and for delineating the appropriate treatment. It is based on histologic evidence of amyloid deposits and characterization of the amyloidogenic protein. We prospectively evaluated the diagnostic performance of immunoelectron microscopy (IEM) of abdominal fat aspirates from 745 consecutive patients with suspected systemic amyloidoses. All cases were extensively investigated with clinical and laboratory data, with a follow-up of at least 18 months. The 423 (56.8%) cases with confirmed systemic forms were used to estimate the diagnostic performance of IEM. Compared with Congo-red-based light microscopy, IEM was equally sensitive (75% to 80%) but significantly more specific (100% vs 80%; P < .001). In amyloid light-chain (AL) amyloidosis, κ cases were more difficult to diagnose (sensitivity 71%), whereas the analysis of abdominal aspirate was informative in only 40% of patients with transthyretin amyloidosis. We found a high prevalence (20%) of a monoclonal component in patients with non-AL amyloidosis, highlighting the risk of misdiagnosis and the need for unequivocal amyloid typing. Notably, IEM identified correctly the specific form of amyloidosis in >99% of the cases. IEM of abdominal fat aspirates is an effective tool in the routine diagnosis of systemic amyloidoses.

Nasal mucosa: a new site for tissue biopsy to diagnose hereditary TTR amyloidosis

BACKGROUND AND OBJECTIVE

We report 2 carriers of the TTRV30M mutation and its plasmatic biochemical marker with clinical symptoms compatible with hereditary TTR amyloidosis.

MATERIALS AND METHODS

Based on our previously reported casual finding of amyloid TTR in nasal mucosa (2008), we requested biopsy of this tissue to search for amyloid with Congo red staining and TTR immunohistochemical analysis.

RESULTS

The histological diagnosis was achieved by retrospective analysis of surgical sinonasal biopsy in the first patient and prospective biopsy of inferior nasal concha in the second. Large interstitial deposits of ATTR were observed in both cases.

CONCLUSIONS

We suggest nasal mucosa as a suitable site for tissue biopsy in patients with suspected hereditary TTR amyloidosis.

In vitro binding of [³H]PIB to human amyloid deposits of different types

Systemic amyloidosis is caused by extracellular deposition of insoluble fibrillar proteins arranged in β-pleated sheets. [(11)C]PIB has been used in PET studies to assess Aβ deposition in brain of patients with Alzheimer's disease (AD). The possibility to visualize other types of amyloid deposits with [(11)C]PIB would be of potential clinical importance in early diagnosis and for following therapeutic effects. In the present study, we evaluated in vitro binding of [(3)H]PIB to tissues containing transthyretin (ATTR), immunoglobulin light-chain (AL), amyloid protein A (AA) and Aβ amyloid. We found significantly higher binding of [(3)H]PIB in tissue from systemic amyloidoses than in control tissue, i.e. 4.7 times higher (p < 0.05). [(3)H]PIB showed the highest affinity to cortex of AD brain (IC50 = 3.84 nM), while IC50 values were much higher for ATTR, AA and AL type of amyloidosis and large variations in affinity were observed even within tissues having the same type of amyloidosis. Extraction with guanidine-HCl, which disrupts the β-sheet structure, decreased the protein levels and, concomitantly, the binding of [(3)H]PIB in all four types of amyloidoses.