Emer Joyce
Consultant Cardiologist, Mater University Hospital
Transthyretin Amyloidosis (ATTR) is a multisystemic condition, typically presenting with heart and/or neuropathy symptoms. It is being increasingly recognised in older people due to heightened awareness and advances in cardiac imaging techniques for diagnosis.
Amyloidosis is a general term used to describe a group of diseases where a particular protein ‘misfolds’ and subsequently accumulates into ‘amyloid fibrils’ which get deposited into various tissues and organs, interrupting their normal function and causing progressive disease.
Risk in older people
In ATTR amyloidosis, transthyretin — a normally occurring protein with important roles in the body — misfolds into fibrils as it exits the liver which deposit in the heart and nerves. It is subdivided into two types: genetic (which we call hereditary ATTR) or acquired (which we call wild-type ATTR).
Wild-type ATTR typically affects older adults, presenting after the sixth decade of life and most commonly in those above 70 years.
In the nervous system, the ATTR amyloid fibrils can cause numbness and tingling.
Because many of its initial manifestations can overlap with more common cardiac conditions such as high blood pressure, it has historically been underdiagnosed.
Hereditary ATTR amyloidosis is caused by a genetic mutation in the TTR gene. While rare, there is a particular variant dominant in Ireland (‘T60A’ or ‘Donegal Amy’). However, over 120 mutations have been described across the world.
Effective therapies have recently emerged for both genetic and wild-type subtypes.
Symptoms and signs
The heart and nervous system are the most frequently involved organs. Patients can present with heart failure syndrome or rhythm problems such as irregular heartbeat or slow heartbeat, which can lead to collapse or dizziness. In the nervous system, the ATTR amyloid fibrils can cause numbness and tingling.
Frequently, patients will have a history of carpal tunnel syndrome (trapped nerve-causing pins and needles) in both hands — often many years before their ATTR amyloidosis diagnosis.
The ‘autonomic’ nervous system can also be affected. Low blood pressure, diarrhoea or constipation and erectile dysfunction can occur.
How is it diagnosed?
The initial suspicion of ATTR amyloidosis is typically based on an echocardiogram (heart ultrasound) and/or cardiac MRI scan.
A definitive diagnosis can then be made through a non-invasive pathway, using blood tests to out-rule any blood cell abnormalities, followed by a special type of bone scan known in short-hand as a ‘DPD scan.’ In more complex cases, a biopsy-led diagnosis may be required.