Carpal Tunnel Syndrome in Transthyretin Cardiac Amyloidosis: Implications and Protocol for Diagnosis and Treatment

Amyloidosis is a group of disorders that occurs due to the aggregation of insoluble and misfolded proteins in the extracellular space, eventually resulting in organ dysfunction. Type II amyloidosis is caused by the deposition of transthyretin (TTR), which will be the main focus of this article. Deposition of TTR in the myocardium results in a restrictive form of cardiomyopathy. TTR can also deposit in the flexor tenosynovium resulting in carpal tunnel syndrome (CTS). CTS develops five to ten years prior to cardiac amyloidosis (CA), and therefore, the temporal relationship allows CTS to be a diagnostic indicator for CA. This report discusses a 65-year-old female and a 76-year-old male, both presenting with pain and paresthesia in the distribution of the median nerve in the left and right wrist. In each case, the diagnosis of bilateral CTS was supported by a positive Phalen's maneuver and Tinel's sign. Subsequent tenosynovial and transverse carpal ligament biopsies were performed with Congo red stain revealing amyloid deposits of TTR monomers. This prompted the investigation into possible cardiac involvement. Following cardiac evaluation, the diagnosis of CA was established for the deposition of TTR amyloid monomers. CA has gained much attention in the medical community due to the improvements in cardiac imaging, therapeutic interventions, and diagnostic indicators. Medical professionals should be urged to have a high level of clinical suspicion and refer patients with CTS and select risk factors for cardiac evaluation.