Ultrasound findings in Transthyretin Familial Amyloidosis Polyneuropathy



Poster Number: T406


Jeffrey Blakesley, DO, University of Wisconsin-Madison Hospital, Stephanie Gardon, MD, University of Wisconsin-Madison Hospital, Michael Hansen, MD, University of Wisconsin-Madison Hospital

Transthyretin Familial Amyloidosis (TTR-FA) is a rare cause of peripheral polyneuropathy with a global prevalence estimated at approximately 10,000 cases. This condition is a multisystem genetic disorder secondary to TTR gene mutation and characterized by the deposition of extracellular transthyretin derived amyloid complexes within multiple organs, including peripheral nerves. We present a case of a 66 year old Caucasian male who presented with two years of progressive distal symmetric pain, numbness, and tingling in upper and lower extremities. Examination was notable for distal sensory loss, distal weakness and muscle atrophy, and diminished distal reflexes in the lower limbs more than upper limbs. EMG/NCS confirmed a severe distal sensorimotor polyneuropathy, with both demyelinating and axonal characteristics. Neuromuscular ultrasound showed enlarged brachial plexuses. Initial lab workup for reversible causes was unremarkable. The patient was started on IVIG empirically due to concern of an immune mediated polyneuropathy (CIDP). Following lack of clinical improvement with IVIG, genetic testing and nerve/muscle biopsy was pursued which confirmed a diagnosis of TTR-amyloid polyneuropathy. The patient was started on Vutrisiran (Amvuttra) treatment and continues with ongoing physical and occupational therapies. This case illustrates a less common pattern of neuromuscular ultrasound findings of predominantly non-entrapment site enlargement of bilateral brachial plexuses in a case of genetically and biopsy confirmed TTR-FAP. Genetic testing and nerve/muscle biopsy play an important confirmatory role in diagnosis of TTR-FAP to guide treatment. Additional evaluation of this multi-system disease entity, particularly with cardiac screening, is an important point in management as this is a common co-occurring manifestation in addition to peripheral polyneuropathy. Co-management of patients by neurologists, cardiologists, and other specialists is common.