TRANSTHYRETIN FAMILIAL AMYLOID POLYNEUROPATHY – THREE HUNGARIAN CASES WITH RARE MUTATIONS (His88Arg AND Phe33Leu)

Introduction - Transthyretin familial amyloid polyneuropathy is a rare autosomal dominant progressive systemic disesase of adults caused by endoneural amyloid deposition due to point mutations of the transthyretin gene. It is the most severe form among hereditary polyneuropathies, being fatal within 10 years if left untreated. The disease is underdiagnosed, the late onset forms (above the age of 50) being probably more widespread than previously thought. Early diagnosis is essential as the early introduction of causal therapy (tafamidis) slows progression and prolongs survival. Patients - We report here three non-related Hungarian cases of transthyretin familial amyloid polyneuropathy with non-Val30Met mutations (His88Arg in two cases, Phe33Leu in one case). They were all characterized by late-onset, progressive, length-dependent, axonal, sensorimotor polyneuropathy and the simultaneous presentation of severe restrictive cardiomyopathy. In all three cases, clinical and electrophysiological signs of myopathy were also present, suggesting the involvement of skeletal muscles as well. In two cases, high resolution ultrasound of the peripheral nerves was also performed, which showed segmental structural alterations (change or loss of fascicular structure) and some increase of echogenicity of the interfascicular epineurium, without substantial enlargement of the nerves. Conclusion - In Hungary, mainly the rare, non-Val30Met mutation forms of transthyretin familial amyloid polyneuropathy are encountered, as in our cases. As opposed to the Val30Met forms, these mutations are characterized by late onset and simultaneous presentation of severe cardiomyopathy. Our report highlights the importance of considering transthyretin familial amyloid polyneuropathy in the differential diagnosis of late-onset, progressive, axonal polyneuropathies of unknown etiology, particularly if associated with cardiac disease.