Amyloidosis

Question 1

What is amyloidosis?

Answer 1

A complex group of disorders caused by the deposition of extracellular, insoluble fibrils composed of misfolded proteins in organs and blood vessels, leading to organ dysfunction.

Question 2

Typical patient for amyloidosis?

Answer 2

It is more common in men than in women and typically presents in the fifth to seventh decade of life.

Question 3

What are the 2 types of amyloidosis?

Answer 3

Primary (AL amyloidosis)

Secondary (AA amyloidosis)

Question 4

Aetiology of AL amyloidosis?

Answer 4

Primary (or AL) Amyloidosis is caused by the deposition of monoclonal light chains (from abnormal plasma cells) in the tissues

It can occur spontaneously or in association with multiple myeloma or Waldenström’s macroglobulinaemia

Question 5

Aetiology of AA amyloidosis?

Answer 5

Secondary amyloidosis (AA amyloidosis) is due to underlying chronic inflammatory conditions

Particularly associated with:

Malignancy
Chronic microbial infection

Question 6

Features of AL amyloidosis?

Answer 6

Proteinuria with and without nephrotic syndrome, plus uraemia – 50% of patients die of renal failure if not treated with dialysis

Visceromegaly (spleen, liver and kidneys) is common

Question 7

Features of AA amyloidosis?

Answer 7

Nephrotic syndrome (one-third of patients)

Neuropathy (usually sensory and symmetrical)

Cardiomyopathy (usually restrictive in nature)

Hepatomegaly (enlarged liver)

Autonomic neuropathy

Question 8

Main diagnostic method of amyloidosis and the main characteristics?

Answer 8

The diagnosis of Amyloidosis requires a tissue biopsy that shows apple-green birefringence when stained with Congo red and viewed under polarised light

Question 9

What are the features of an amyloidosis tissue biopsy?

Answer 9

A biopsy is often taken from the rectum with a sensitivity of 74–94%

Biopsies can also be performed by fine-needle aspiration from fat and bone marrow

A positive yield is achieved in around 80% of cases

Question 10

What are some other investigations that can be used for amyloidosis?

Answer 10

Echocardiography, ECG and brain natriuretic peptide (BNP) – to assess cardiac function

Proteinuria (24-hour urine collection), renal and liver function

Serum-free light chains or monoclonal immunoglobulins – found in 99% of patients with AL Amyloid

Prothrombin time (PT) and activated partial thromboplastin (APTT) – prolonged owing to factor 10 absorption into amyloid fibrils in the spleen