Transthyretin (TTR) amyloidosis is an autosomal dominant disorder caused by the deposition of insoluble amyloid fibrils around peripheral nerves and in various tissues, including the heart muscle. Based on the predominant organ involvement, several distinct subtypes have been reported.
Familial amyloid polyneuropathy (FAP) aka TTR amyloid neuropathy is characterized by slowly progressive, peripheral sensorimotor polyneuropathy and autonomic dysfunction. Disease onset is usually in the third to fourth decade of life. Sensory neuropathy starts in the lower extremities with paresthesia, impaired pain and temperature sensation, followed by loss of motor function. Autonomic neuropathy usually manifests with orthostatic hypotension, constipation alternating with diarrhea, vomiting, impotence or hypohidrosis. Unrelated to neuropathy, other organs manifestations may include cardiomyopathy, vitreous opacities and CNS amyloidosis.
Leptomeningeal amyloidosis aka oculoleptomeningeal amyloidosis affects predominantly the central nervous
system, sometimes combined with visual impairment.
Cardiac amyloidosis usually manifests in the sixth decade of life with progressive left ventricular hypertrophy and restrictive cardiomyopathy. In a subset of families with cardiac amyloidosis, peripheral neuropathy may be completely absent or very mild.
Treatment: Currently, the only effective treatment for FAP is an orthotopic liver transplant to stop production of misfolded amyloid protein. In patients with severe amyloid cardiomyopathy, a heart transplant may be
necessary. Different drugs designed to prevent or alleviate accumulation of TTR amyloid protein (transthyretin amyloidois inhibitors) are currently under investigation.