Hereditary amyloidosis

In the case of hereditary amyloidoses, the existence of a family history or similar illness is of great assistance in diagnosing the condition. However, not everyone with a mutation in a gene associated with hereditary amyloidosis will develop symptoms. Additionally, symptoms of the disease typically do not appear until older age and the condition may have been misdiagnosed in other affected family members. For these reasons, the absence of a family history may be misleading.

The diagnosis of amyloidosis is usually made by performing a tissue biopsy and staining the tissue with Congo red stain to detect the presence or absence of amyloid deposits. The biopsy may be from any affected organ, but biopsying the rectal mucosa generally results in better detection of the following hereditary amyloidoses: transthyretin amyloidosis, apolipoprotein AI amyloidosis, fibrinogen Aα-chain amyloidosis (A Fib), and apolipoprotein AII amyloidosis (A ApoAII).

Additionally, when a hereditary amyloidoses is suspected, genetic testing may be able to confirm a diagnosis. It is important to note that genetic testing may not be available for all types of hereditary amyloidoses. For those individuals interested in pursuing genetic testing, we recommend scheduling a genetics consultation to determine whether genetic testing would be appropriate and available.

The hereditary amyloidoses are inherited in an autosomal dominant manner. This means that one altered copy of the disease-causing gene (called a mutation) in each cell is sufficient to cause the disease. The disease-causing mutation can be inherited from a parent or it can occur for the first time in an individual. Each child of an individual affected with hereditary amyloidosis has a 50% (1 in 2) risk to inherit the disease-causing mutation and a 50% chance of not inheriting the mutation. However, not all individuals with a mutation in a gene that causes hereditary amyloidosis will develop signs and symptoms of the disease.

Hereditary amyloidosis refers to a group of inherited conditions that make up one of the subtypes of amyloidosis. Hereditary amyloidosis is characterized by the deposit of an abnormal protein called amyloid in multiple organs of the body where it should not be, which causes disruption of organ tissue structure and function. In hereditary amyloidosis, amyloid deposits most often occur in tissues of the heart, kidneys, and nervous system. While symptoms of hereditary amyloidosis may appear in childhood, most individuals do not experience symptoms until adulthood. There are many types of hereditary amyloidosis associated with different gene mutations and abnormal proteins. The most common type of hereditary amyloidosis is transthyretin amyloidosis (ATTR), a condition in which the amyloid deposits are most often made up of the transthyretin protein which is made in the liver. Other examples of hereditary amyloidosis include, but are not limited to, apolipoprotein AI amyloidosis (A ApoAI), gelsolin amyloidosis (A Gel), lysozyme amyloidosis (A Lys), cystatin C amyloidosis (A Cys), fibrinogen Aα-chain amyloidosis (A Fib), and apolipoprotein AII amyloidosis (A ApoAII). Most types of hereditary amyloidosis are inherited in an autosomal dominant manner. Treatment is focused on addressing symptoms of organ damage and slowing down the production of amyloid when possible through methods such as liver transplants.

The Mayo Clinic provides information on the diagnosis and treatment of amyloidosis.