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A 55-year-old man with peripheral neuropathy and autonomic dysfunction develops heart failure. His father had similar symptoms and died in his 60s. Genetic testing reveals a TTR mutation.
AD; TTR (transthyretin)
- Val122Ile common in African Americans
- Val30Met common in endemic areas (Portugal, Sweden, Japan)
- Progressive sensorimotor polyneuropathy
- Cardiomyopathy (restrictive/infiltrative)
- Autonomic dysfunction (orthostatic hypotension, GI, erectile dysfunction)
- Vitreous opacities
- Tissue biopsy shows amyloid with Congo red apple-green birefringence under polarized light; mass spectrometry or immunohistochemistry types the deposit to distinguish ATTR from AL amyloidosis
- Technetium pyrophosphate (Tc-99m PYP) cardiac scintigraphy is highly sensitive and specific for ATTR cardiac amyloid and can confirm it noninvasively
- TTR sequencing distinguishes hereditary (variant) ATTR from wild-type, age-related ATTR and enables cascade testing
- Tafamidis (TTR stabilizer), patisiran/inotersen (TTR silencers), liver transplant (selected cases)
"Trans-thy-retin": The protein name tells you its function: it TRANSports THYroid hormone and RETINol (vitamin A) in the blood. When it misfolds, it forms amyloid deposits in the heart and nerves