Autonomic and Gastrointestinal Manifestations of hATTR Polyneuropathy

Key Takeaways:

• hATTR-PN is a multisystem disease. Autonomic neuropathy is common and may be an early clue to the diagnosis, yet it is often overlooked.
• Gastrointestinal involvement is common, may precede the neuropathy, and contributes substantially to quality of life and nutritional decline.
• Because these manifestations span multiple organ systems, early recognition supports both the diagnosis and the multidisciplinary, supportive care the disease requires.

Hereditary transthyretin amyloidosis with polyneuropathy (hATTR-PN) is often described as a length-dependent sensorimotor neuropathy, but the disease extends well beyond the somatic peripheral nerves. Autonomic neuropathy is a defining feature, present in approximately 73 percent of patients, and is frequently overlooked during the initial evaluation.¹

For neurologists, autonomic and gastrointestinal (GI) manifestations are simultaneously a diagnostic asset – because they help separate amyloid neuropathy from its mimics – and a management challenge that reaches well beyond the peripheral nerve.

Autonomic dysfunction as a red flag

Autonomic symptoms occurring alongside an otherwise unexplained polyneuropathy should raise suspicion for hATTR-PN. Among affected patients:¹

• Erectile dysfunction affects approximately 73 percent of males
• Urinary incontinence approximately 50 percent
• Orthostatic dysregulation approximately 46 percent

Dysautonomia in a patient with an otherwise unexplained axonal polyneuropathy should prompt consideration of hATTR-PN, even in older adults without a known family history.²

Phenotype matters here: Patients with early-onset Val30Met disease often develop prominent autonomic symptoms early, while autonomic involvement in late-onset disease may be milder initially or develop later. The absence of marked dysautonomia should not exclude the diagnosis.¹

The gastrointestinal burden

GI dysfunction is one of the most common manifestations of autonomic involvement in hATTR-PN and is a major contributor to reduced quality of life.³

The pattern is characteristic: Common symptoms include unintentional weight loss, early satiety, alternating diarrhea and constipation, nausea, and vomiting. Unintentional weight loss may develop early and, in some patients, precedes obvious gastrointestinal or neurologic symptoms.³

GI involvement is also associated with worse outcomes. Earlier onset of diarrhea has been linked to shorter survival.^1,3

Avoiding diagnostic and management pitfalls

Several diagnostic considerations are worth keeping in mind. Routine endoscopic mucosal biopsies may be nondiagnostic because amyloid deposition is largely submucosal. Biopsies that include the submucosa are more likely to identify amyloid deposition.³

Second, GI bleeding and mechanical obstruction are not expected features of amyloid enteropathy, so these presentations warrant investigation for a separate, non-amyloid cause. Management is largely supportive and mechanism-directed:³

• Prokinetic agents for gastroparesis
• Antibiotics when small intestinal bacterial overgrowth (SIBO) is suspected
• Osmotic laxatives for slow-transit constipation
• Antidiarrheal agents for rapid transit

Because controlled trials in this population are limited, most of these approaches are extrapolated from related enteropathies and should be individualized. Modified BMI (BMI × serum albumin) is a useful marker of nutritional status and has been associated with both neurologic function and survival.³

Coordinating multidisciplinary care

Because hATTR-PN affects multiple organ systems, management often requires close collaboration between neurology, gastroenterology, cardiology, and, when appropriate, autonomic specialists and urology.¹

Although disease-modifying therapies slow disease progression, supportive treatment for autonomic and gastrointestinal symptoms remains an important part of care. Where disease-modifying therapy is indicated, treatment includes gene-silencing agents and TTR stabilizers. However, supportive treatment of autonomic and gastrointestinal symptoms remains essential, as these manifestations often persist despite disease-modifying therapy.³

Recognizing autonomic and gastrointestinal involvement early can help establish the diagnosis sooner and ensure patients receive the multidisciplinary care these complex manifestations require.