Amyloidosis is a complex disease
characterized by deposition of insoluble aggregates of misfolded proteins between the heart cells. It can also be hereditary.
There are several forms of Amyloidosis, each of which is due to a specific defective protein, which can affect numerous organs, particularly the heart, kidneys and nervous system.
Cardiac involvement has various forms, but two are the main ones:
- AL amyloidosis, systemic non-hereditary form, often due to excessive production of protein from bone marrow cancer (myeloma)
- ATTR amyloidosis (from transthyretin) a protein produced by the liver which carries retinol and thyroid hormones in the blood.
ATTR amyloidosis related to deposition of Transthyretin comes in two forms:
- a shape non-hereditary form which almost always affects only the heart, in subjects over 60 years of age, also called senile or wild-type cardiac amyloidosis.
- a shape hereditary form in which the amyloid deposits, depending on the specific genetic mutation, can affect the heart or the peripheral nervous system or both areas. It begins to manifest after the age of 40.
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Deposition of amyloid fibrils between heart cells is progressive and leads to an increase in thickness of the walls of the heart, including the atria, which mimic Hypertrophic Cardiomyopathy (HCM). Amyloid progressively damages the functioning of heart cells. The walls become more rigid and their relaxation is very slow ("Diastolic dysfunction") and finally, contraction force also reduces ("Systolic dysfunction"). Symptoms such as palpitations and dyspnea, absent at the beginning, are progressive, with the appearance of atrial and ventricular arrhythmias up to congestive heart failure.
In recent years, with the increase in knowledge and diagnostic tools, such as scintigraphy with bone tracers, genetic analysis and Strain evaluation by Echocardiography, it is possible to distinguish sarcomeric HCM from ATTR amyloidosis, both in the senile and in the hereditary form.
In patients over the age of 60 with HCM, ATTR amyloidosis is far from being a rare disease.
The importance of genetic analysis
Genetic analysis of the patient with amyloidosis allows to identify the hereditary form and to assess whether it is also present in family members. This may allow for innovative drug therapy that can block the development of amyloid deposits and subsequent complications.
In Italy there are areas (e.g. Tuscan-Romagnolo Apennines) where hereditary ATTR amyloidosis is more frequent, due to a specific mutation passed down over centuries by inheritance.
The heart with ATTR cardiac amyloidosis is clearly visualized by scintigraphy with bone tracers.