Alnylam Act^® hATTR Amyloidosis Sponsored Testing Program

Hereditary ATTR amyloidosis (hATTR amyloidosis) is an inherited, rapidly progressive, debilitating, and fatal disease. It is caused by a variant in the transthyretin (TTR) gene that results in misfolded TTR proteins accumulating as amyloid fibrils in multiple tissues including the nerves, heart, and gastrointestinal tract. hATTR amyloidosis can lead to significant morbidity, disability, and mortality, with a median survival of 4.7 years following a diagnosis.

hATTR amyloidosis is a multisystemic disease with a heterogeneous clinical presentation that includes sensory and motor neuropathy, autonomic neuropathy (e.g., diarrhea, sexual dysfunction, orthostatic hypotension), and cardiac symptoms.

Pathogenic variants in the TTR gene are inherited in an autosomal dominant manner with incomplete penetrance (Sekijima. 2018. PubMed ID: 20301373). Homozygosity has been reported in a few cases with higher penetrance, with patients having earlier onset and greater severity of disease compared with heterozygotes (Albenque et al. 2023. PubMed ID: 37377439). Other genes associated with hereditary amyloidosis include FGA, B2M, LYZ and APOA1.

Missense changes found throughout the TTR gene account for >95% of the causative variants. Specific missense changes are associated with neuropathic, cardiac, or leptomeningeal amyloidosis forms, but phenotypic overlap can occur. There are two primary founder variants, c.148G>A (p.Val50Met) and c.424G>A (p.Val142Ile). These variants are also referred to as p.Val30Met and p.Val122Ile using legacy nomenclature. The p.Val50Met variant has been found in 1 in 538 northern Portuguese with penetrance of 80% by age 50, 4% of northern Swedes with penetrance of 11% by age 50, and in 1 in 100,000 Nagano Japanese (Ando et al. 2013. PubMed ID: 23425518; Sekijima et al 2018. PubMed ID: 29343286). Neuropathic ATTR is primarily found in individuals with the p.Val50Met variant in early stages with cardiac and kidney dysfunction. Transgenic mice expressing the p.Val50Met variant present with amyloidosis leading to gastrointestinal, cardiac, and kidney dysfunction (Yi et al. 1991. PubMed ID: 1992765). The p.Val142Ile variant is found in ~3.5% of African Americans with age-dependent penetrance and has been found in 10% of African Americans over 65 years of age with severe congestive heart failure (Buxbaum and Ruberg. 2017. PubMed ID: 28102864).

The TTR gene encodes transthyretin, which functions in transport of retinol (vitamin A) and thyroxine (thyroid hormone) when present as a homotetramer (Ando et al. 2013. PubMed ID: 23425518). The TTR gene is not essential for viability of tissue culture cells. Homozygous TTR knockout mice have decreased susceptibility to AMPA-induced neurodegeneration (Nunes et al. 2009. PubMed ID: 19595729).

This test is performed using Next-Gen sequencing with additional Sanger sequencing as necessary. This test provides full coverage of all coding exons of the TTR gene plus 10 bases of flanking noncoding DNA in all available transcripts along with other non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define full coverage as >20X NGS reads or Sanger sequencing.

To learn more about our test methods and limitations, please CLICK HERE.

Patients with at least one hATTR high index of suspicion indicators (below) are eligible for testing:

• Family history of hATTR amyloidosis
• Positive imaging consistent with amyloid (technetium, CMR, strain echo)
• Positive biopsy for TTR amyloid

OR

Patients with at least two hATTR index of suspicion indicators (below) are eligible for testing:

• Sensory and/or motor neuropathy (e.g., neuropathic pain, altered sensation, numbness and tingling, muscle weakness, impaired balance, difficulty walking, carpal tunnel syndrome-associated neuropathy, EMG/NCS abnormalities)
• Autonomic dysfunction (e.g., nausea and vomiting, changes in GI motility, orthostatic hypotension, sexual dysfunction, bladder dysfunction)
• Heart disease (e.g., cardiomyopathy, restrictive physiology, hypertrophy, arrhythmias, conduction abnormalities, heart failure, abnormal cardiac imaging)
• Musculoskeletal indicators (e.g., history of carpal tunnel syndrome, back pain/lumbar spinal stenosis, rotator cuff injury)
• Renal abnormalities (e.g., renal insufficiency and/or proteinuria)
• Ocular changes (e.g., vitreous opacity, glaucoma, dry eyes, ocular amyloid angiopathy, retinal detachment)

Individuals in the US and Canada tested through the Alnylam Act^® program are eligible for optional pre- and post-test genetic counseling to help them understand their test results. This service is provided through GenomeMedical, a third-party genetic counseling service, and is made available by Alnylam at no charge as part of the program.

Pre-test genetic counseling is intended to help the patient learn more about what to expect during the genetic testing process. If the patient receives a negative test result, Genome Medical will provide an educational video explaining the results.

Patients can access genetic counseling by having their healthcare provider complete the pre- and/or post-test genetic counseling section of the PreventionGenetics test requisition form.

Patients will be contacted by GenomeMedical to schedule an appointment, generally within 24-48 hours of receipt of the faxed referral form.

SPECIMEN REQUIREMENTS

Whole Blood

Collect 3 ml - 5 ml of whole blood in EDTA (purple top tube) or ACD (yellow top tube).

Saliva

Oragene™ or GeneFiX™ Saliva Collection kit used according to manufacturer instructions. DNA from saliva specimens is invariably contaminated with microbial and food DNA, which can impact specimen quality and may result in delayed testing and/or the need for a second specimen.

OCD-100 Swab

OCD-100 Buccal Swab used according to manufacturer instructions.

Buccal

Specimens may be shipped at room temperature.

Specimen collection kits: Buccal specimen collection kits, which contain the TRF and the shipping label, may be requested through the kit order form or via the online order form.

SHIPPING AND HANDLING INSTRUCTIONS

Label all specimen containers with the patient's name, date of birth, and/or ID number. At least two identifiers should be listed on specimen containers. Specimen deliveries are accepted Monday-Saturday for all specimen types. Holiday schedules will be posted on our website at least one week prior to major holidays.