Differentiating ATTR-CM and PN

Summary for Physicians: Differences in Diagnosis Between ATTR-CM and ATTR-PN

1. ATTR-CM (Transthyretin Amyloid Cardiomyopathy):

• Primary organ involvement: ATTR-CM primarily affects the heart, leading to restrictive cardiomyopathy with symptoms of heart failure, arrhythmias, and sometimes conduction abnormalities.
• Diagnostic approach:
  • Clinical presentation: Patients typically present with heart failure symptoms, arrhythmias (including atrial fibrillation), and brady/tachy arrhythmias.
  • Cardiac biomarkers: Elevated NT-proBNP and cardiac troponins
  • Imaging: Echocardiography and cardiac MRI can show thickened heart walls, restrictive filling patterns, and amyloid deposits.
  • Genetic testing: Identifying mutations in the TTR gene can confirm hereditary forms of ATTR-CM.
  • Tissue biopsy/scintigraphy: Confirmation can be done through tissue biopsy showing amyloid deposits or using bone scintigraphy (with technetium-labeled agents).

2. ATTR-PN (Transthyretin Amyloid Polyneuropathy):

• Primary organ involvement: ATTR-PN predominantly affects the nervous system, leading to peripheral neuropathy, autonomic dysfunction, and sometimes carpal tunnel syndrome (CTS).
• Diagnostic approach:
  • Clinical presentation: Patients often present with sensory and motor neuropathy, pain, numbness, and weakness, typically in the distal limbs. They may also have autonomic symptoms, such as orthostatic hypotension or gastrointestinal dysfunction.
  • Nerve conduction studies: Can detect slowed nerve conduction and reduced amplitude, confirming neuropathy
  • Electromyography: Used to assess the extent of motor involvement in the peripheral nerves
  • Genetic testing: Like ATTR-CM, genetic testing for TTR mutations is essential for confirming the hereditary form of ATTR-PN.
  • Tissue biopsy: Similar to ATTR-CM, a biopsy may be performed to confirm amyloid deposits in the peripheral nerves.

Key Differences in Diagnosis:

• Organ system affected: ATTR-CM primarily affects the heart, whereas ATTR-PN affects the peripheral nervous system. However, both can share extracardiac manifestations such as CTS.
• Symptoms: ATTR-CM presents mainly with cardiac symptoms (heart failure, arrhythmias), whereas ATTR-PN presents with neurological symptoms (numbness, pain, weakness).
• Diagnostic testing: Although both conditions can be confirmed via genetic testing for TTR mutations, scintigraphy and tissue biopsy help identify amyloid deposits in the heart for ATTR-CM and in the nerves for ATTR-PN.

Understanding these differences is crucial for accurate diagnosis and ensuring proper treatment tailored to each condition.