A. Introduction [2]

1. Definition
   1. Amyloid refers to tissue deposits of protein fibrils
   2. On normal microscopy, these fibrils appear as amorphous eosinophilic material
   3. The fibrils have a specific appearance with special stains (see below)
   4. Immunohistological staining is required to determine component(s) of amyloid
2. Fibril Subunits
   1. Subunits are usually not actual ß-pleated sheets as originally thought
   2. Instead, they are globular structures
   3. Held together by non-covalent bonds in paired fibrillar arrays
3. Protein Composition
   1. Amyloid P Protein: an alpha-glycoprotein found in all deposits
   2. Second protein is always present and depends on underlying cause of illness
   3. Ig L chains are most common type of second chain (AL)
   4. Amyloidogenic proteins interact with glycosaminoglycans (GAGs) in extracellular matrix (ECM)
   5. These interactions lead to polymerization of amyloidogenic fibrils and disruption of normal ECM architecture causing organ dysfunction
4. Major Types of Amyloid Proteins
   1. Immunoglobulin (Ig) Light (L) chains - component in AL (primary) amyloidosis
   2. Amyloid A Protein - component in AA (secondary) amyloidosis
   3. Prealblumin (transthyretin, ATTR) - most common hereditary type
   4. Apudamyloid - association with neuroendocrine tumors (such as medullary thyroid cancer)
   5. ß2-microglobulin - renal failure associated amyloid
   6. Apolipoprotein A-I, fibrinogen Aa and lysozyme can also form fibrils
   7. Pancreatic islet amyloid
   8. Gelsolin
5. Epidemiology
   1. Overall incidence of Primary amyloidosis is ~10 cases per million person years
   2. For primary amyloidosis, this means about 2500 new cases in USA per year
   3. ATTR hereditary type is second most common in USA with 250-500 new cases/year
   4. Secondary amyloidosis is least common
   5. Amyloidosis is diagnosis in ~2.5% of renal biopsies
   6. Cause of death in ~1 per 1500 persons

B. Types of Amyloid [2]

1. Acquired Monoclonal Ig-L Chain Amyloidosis (AL) [28]
   1. Formerly called "primary" amyloidosis
   2. Associated with plasma cell dyscrasias
   3. Most often associated with myeloma (MM), occasionally isolated plasmacytoma
   4. Benign Monoclonal Gammopathy (including MGUS) or
   5. Waldenstrom's Macroglobulinemia
   6. L chains usually of the Lambda subclass
   7. Most L chain Igs are not amyloidogenic; 10-15% of MM associated with AL
   8. Serum amyloid P component (SAP) frequently associates with AL chains
2. Reactive Serum Amyloid A (SAA) Amyloidosis [11]
   1. Chronic inflammatory disease predispose to this type of amyloidosis
   2. SAA is synthesized by hepatocytes with other acute phase proteins
   3. Synthesis stimulated by IL-1, IL-6, TNF alpha, others
   4. SAA normally exists as ~6 heterogeneous molecular forms
   5. SAA binds to HDL3 particles along with LPS (may assist endotoxin clearance)
   6. Main consideration in differential diagnosis of AL form
   7. Over time, renal dysfunction is predominant manifestation
   8. Amyloid burden, renal disease, and mortality all correlated
   9. Highest 12% of SAA serum levels associated with 17X risk of death versus lowest 12%
   10. Amyloid deposits can regress (~60% of cases) during course of disease
   11. Regressed amyloid levels associated with improved outcomes
   12. Median survival in large cohort 133 months
3. Common Causes of Secondary Amyloidosis
   1. Mycobacterial infection
   2. Collagen vascular diseases - especially rheumatoid arthritis
   3. Crohn's diseases
   4. Familial Mediterranean Fever (FMF)
4. Uncommon Causes of Secondary Amyloidosis
   1. Chronic supperative conditions
   2. Hodgkin Disease
   3. Renal cell carcinoma
5. ß2-Microglobulin Amyloidosis [27]
   1. Deposition: shoulders, carpal tunnels, flexor tendons of hands, tongue (macroglossia)
   2. Periarticular thickening, shoulder pad, nodules, rare cutaneous papules
   3. Amyloid deposition is major pathological finding
   4. Associated with chronic renal failure (CRF)
6. Hereditary (Familial) Amyloid Fibrils [25]
   1. A number of abnormal proteins can form amyloid fibrils
   2. Abnormal transthyretin (ATTR, prealbumin) protein is most common familial form [5,16]
   3. ATTR is autosomal dominant, and >50 single amino acid mutations have been found
   4. Normally synthesized in liver, transthyretin transports thyroxine and retinol
   5. Also made in choroid plexus
   6. Autosomal dominant inheritance with variable age of onset for familial amyloid
   7. Nearly 10% of patients with clinical diagnosis of AL have mutations in genes associated with hereditary amyloidosis [25]
7. Islet Amyloid [20]
   1. Amyloid deposition in islets contributes to pathogenesis of type 2 diabetes mellitus (DM 2)
   2. This amyloid is composed mainly of 37-residue peptide called islet amyloid polypeptide (IAP)
   3. Peptide is coded on chromosome 12
   4. No difference in sequence bewteen normal IAP and that found in amyloid deposits
   5. Specific regions of the human IAP are "amyloidogenic"
   6. IAP expression is controlled by factors similar to those which drive insulin production
   7. Islet amyloid is toxic to ß-cells in the pancreas and is found in 90% of DM 2 patients

C. Manifestations

1. Multisystem Disease
2. Renal insufficiency [3]
   1. Nephrotic syndrome is most common type of renal dysfunction
   2. Progressive reductions in creatinine clearance occur in >50% of patients
   3. Progression to renal failure is common
3. Liver Abnormalities
   1. Hepatomegaly
   2. Mainly obstruction (may have hyperbilirubinemia)
   3. Alkaline phosphatase and 5'-nucleotidase elevations
4. Gastrointestinal Disturbance
   1. Altered motility
   2. Diarrhea
   3. Malabsorption [24]
5. Cardiac
   1. Restrictive Cardiomyopathy - infiltrative disease, biventricular enlargement [17]
   2. Congestive heart failure may ensue and is very difficult to treat [3,23]
   3. Conduction system disease - including heart block, bradycardia
6. Abnormal Skin - diagnosis by (rectal) fat pad biopsy with congo red (and other) stains
7. Pulmonary [6]
   1. Interstitial or reticulonodular pattern [8] - symptomatic in <20% of patients
   2. Pleural effusion was not uncommon
   3. Nodular pulmonary lesions are called "amyloidomas" and are usually benign
   4. Frank alveolitis can occur, with potential (rare) for hematoma formation [16]
8. Peripheral Neuropathy [13,14,15]
   1. Typically painful, sensory neuropathy (paresthesias) due to nerve cell death
   2. Muscle weakness and numbness also occur with amyloidosis
   3. Autonomic neuropathy also occurs in ~2/3 of patients
   4. Mononeuritis multiplex also occurs [21]
   5. Peripheral nerves may regrow with appropriate therapy of familial amyloidosis
   6. Median survival for patients with neuropathy at diagnosis of gammopathy was 25 months
   7. For AL amyloid with neuropathy, albumin level >3 gm/dL had better outcome
9. Central Nervous System [19]
   1. Cerebral amyloid angiopathy (CAA) common finding in autopsy series
   2. Up to 30% of asymptomatic autopsies on geriatric patients
   3. Pathology shows small cortical infarcts, punctate hemorrhage, lobar hemorrhages
   4. Symptoms include lobar hemorrhages [9,18], dementia and/or focal seizures
   5. Chronic encephalopathy with progressive dementia can occur
   6. Risk for initial and recurrent lobar hemorrhage linked to apolipoprotein E genotype
   7. Thus, carriers of Apo E e2 or e4 genotypes had 3.8X increased risk for recurrence [18]

D. Diagnosis

1. All persons with multisystem disease should be suspected
2. Persons with unusual manifestations of chronic inflammatory disease
3. Tissue biopsy is nearly always required
4. Microscopy of Stained Sections defines Amyloid Deposits
5. Stained sections show "apple-green" birefringence on polarization microscopy
   1. Alkaline Congo Red Stain is typically used
   2. Sulfated Alcian Blue may also be used
   3. All types of amyloid deposits appear similar under microscope
6. Immunohistochemistry is require to determine amyloid type
7. In patients with AL amyloidosis, serum albumin level was correlated with outcome [14]

E. Treatment

1. Generally aimed at underlying condition
   1. Generally must distinguish between AL (primary) and secondary disease
   2. Treatment aimed at treating any underlying disease in AL and AA cases
   3. Eprodisate developed for treatment of AA disease
   4. Transplantation of kidney or heart is mainstay for disease of these organs
2. AL Amyloidosis / Plasma Cell Dyscrasias [4,8]
   1. Diagnosis with serum and urine protein electrophoresis
   2. Severe symptoms such as hyperviscosity may be treated with plasmapheresis
   3. Combination therapy is advantageous for non-renal or cardiac disease [10]
   4. Glucocorticoids ± alkylating agents usually used
   5. Melphalan/prednisone combination improves survival from <12 to >17 months in AL [12]
   6. Melphalan may improve cardiac disease in AL amyloidosis [10]
   7. High dose melphalan with autologous stem cell transplant benefit myeloma (M-) component and associated renal disease in primary amyloidosis [22]
   8. Autologous stem cell transplant following melphalan provides median survival 4.6 years [26]
   9. Stem cell transplant may be beneficial but transplant associated mortality increases with number of organ systems affected [4,26]
   10. High dose melphalan with autologous stem cell rescue (survival 22.2 months) was inferior to oral melphalan with high dose dexamethasone (survival 56.9 months) [7]
   11. Patients with cardiomyopathy receiving stem cell transplant have highest mortality [26]
   12. Newer anti-myeloma agents are likely to effective; may be better tolerated
   13. Therefore, consider revlimid, thalidomide, or bortezomib
3. AA Amyloidosis [29]
   1. Treatment of underlying inflammatory disease can sometimes reduce SAA levels
   2. In many cases, however, SAA levels remain high and AA amyloidosis develops
   3. Eprodisate (Kiacta®) is a negatively charged, sulfated low molecular weight compound similar to heparan sulfate
   4. Eprosisate interferes with interactions between amyloidogenic proteins and GAGs
   5. Eprodisate thereby inhibits polymerization of amyloid fibrils and deposition in tissues
   6. Dosed 400-800mg po bid based on increasing renal function
   7. Slowed progression of disease and reduced reductions in creatinine clearance in 2 years
   8. In 2 years, showed trend to reduction in progression to end stage renal disease
4. ATTR Amyloidosis
   1. Liver transplantation is considered definitive therapy [13]
   2. Long term outlook is unknown, but normal thyrotropin is found in blood after transplant
5. Organ specific / supportive therapies for other manifestations
6. Alzheimer's Disease

References

1. Falk RH, Comenzo RL, Skinner M. 1997. NEJM. 337(13):898
2. Merlini G and Bellotti V. 2003. NEJM. 349(6):583
3. Geltman EM and Saffitz J. 1997. Am J Med. 102(5):496 (Case Report)
4. Gertz MA, Lacy MQ, Dispenzieri A, et al. 2002. Am J Med. 113(7):549
5. Jacobson DR, Pastore RD, Yaghoubian R, et al. 1997. NEJM. 336(7):466
6. Utz JP, Swensen SJ, Gertz MA. 1996. Ann Intern Med. 124(3):407
7. Jaccard A, Moreau P, Leblond V, et al. 2007. NEJM. 357(11):1083
8. Kradin RL and Mark EJ. 1996. NEJM. 335(4):266 (Case Report)
9. Greenberg SM and Edgar MA. 1996. NEJM. 335(3):189 (Case Record)
10. Dubrey S, Mendes L, Skinner M, Falk RH. 1996. Ann Intern Med. 125(6):481
11. Lachmann HJ, Goodman HJ, Gilbertson JA, et al. 2007. NEJM. 356(23):2361
12. Kyle RA, Gertz MA, Greipp PR, et al. 1997. NEJM. 336(17):1202
13. Ikeda SI, Takei YI, Yanagisawa N, et al. 1997. Ann Intern Med. 127(8):618
14. Rajkumar SV, Gertz MA, Kyle RA. 1998. Am J Med. 104(3):232
15. Ropper AH and Gorson KC. 1998. NEJM. 338(22):1601
16. Berk IJ and Mark EJ. 1998. NEJM. 338(26):1905 (Case Record)
17. DiSalvo TG, King ME, Smith RN. 2000. NEJM. 342(4):264
18. O'Donnell HC, Rosand J, Knudsen KA, et al. 2000. NEJM. 342(4):240
19. Caplan LR and Louis DN. 2000. NEJM. 342(13):957
20. Hoppener JWM, Ahren B, Lips CJM. 2000. NEJM. 343(6):411
21. Gorson KC, Hedley-Whyte ET, Skinner MM. 2001. NEJM. 344(12):917 (Case Record)
22. Dember LM, Sanchorawala V, Seldin DC, et al. 2001. Ann Intern Med. 134(9):746
23. Sinha MK, Lachmann HJ, Kuriakose B, et al. 2001. Lancet. 357(9267):1498 (Case Report)
24. Hayman SR, Lacy MQ, Kyle RA, Gertz MA. 2001. Am J Med. 111(7):535
25. Lachmann HJ, Booth DR, Booth SE, et al. 2002. NEJM. 346(23):1786
26. Skinner M, Sanchorawala V, Seldin DC, et al. 2003. Ann Intern Med. 140(2):85
27. Moschella SL, Kay J, Mackool BT, Liu V. 2004. NEJM. 351(21):2219 (Case Record)
28. Dember LM, Shepard JO, Nesta F, Stone JR. 2005. NEJM. 352(20):2111 (Case Record)
29. Dember LM, Hawkins PN, Hazenberg BP, et al. 2007. NEJM. 356(23):2349