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Answer
A) ATTR (Transthyretin amyloid)
The answer is ATTR.
Here's the reasoning:
- Age 78, male, no family history - points to wild-type (senile) ATTR amyloidosis, the most common cause of cardiac amyloidosis in elderly men
- Restrictive cardiomyopathy + congo red positive + apple-green birefringence - classic histological hallmark of amyloid deposition
- No family history rules out hereditary/familial ATTR (autosomal dominant mutation) as the primary consideration, making wild-type ATTR most likely
- ATTR (transthyretin protein) is the predominant fibril in senile cardiac amyloidosis
Why not the others?
| Option | Protein | Associated Condition |
|---|---|---|
| ATTR | Transthyretin | Wild-type (elderly men) or familial cardiac amyloid |
| ACal | Calcitonin | Medullary thyroid carcinoma |
| AANF | Atrial natriuretic factor | Isolated atrial amyloid |
| AIAPP | Islet amyloid polypeptide | Type 2 diabetes (pancreatic amyloid) |
The key discriminator here is the clinical triad: elderly man + restrictive cardiomyopathy + no family history = wild-type ATTR cardiac amyloidosis. AL amyloid (from plasma cell dyscrasias) would also be on the differential, but ATTR is the classic answer for this age/sex profile with no family history and no mention of plasma cell disorder.
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