Unusual Case Study: Presentation and Diagnosis of ATTR Amyloid

In recent years, there has been increased awareness of transthyretin amyloidosis (ATTR amyloid), a condition that historically has been an underrecognized cause of nonischemic cardiomyopathy. Noninvasive imaging techniques used for diagnosing ATTR amyloidosis have been among the cutting-edge advances, but myocardial biopsy remains the gold standard and has its risks as an invasive procedure with the potential for high-risk complications.

Pelter and colleagues from Scripps Clinic in La Jolla, CA, described a case study of a 69-year-old male with aortic stenosis and longstanding heart failure who had recently developed bilateral carpal tunnel syndrome. He had an ejection fraction of 45% and had been followed closely in clinic and presented for presurgical cardiac evaluation for the carpal tunnel syndrome. An ultrasound performed at bedside suggested reduced ejection fraction, without evidence of a small left ventricular cavity or granular appearance. However, the echocardiogram did show a 1.9-mm biatrial enlargement of the intraventricular septum and thickened valves. Based on the combination of the carpal tunnel syndrome, the patient’s echocardiographic findings, and known history of heart failure, the clinicians sent a tendon tissue sample from the surgical procedure to pathology for amyloid testing. The sample was stained using H and E stain, Congo red stain, and apple-green birefringence, and returned positive for all 3. The patient was eventually diagnosed with ATTR amyloidosis and treated accordingly.

This case was clinically interesting because the presentation and diagnosis of ATTR amyloid was unusual. The patient did not meet the classical criteria for the condition, including the echocardiographic findings. “Out of the box” thinking revealed the correct diagnosis, and cases such as this will possibly become more common as ATTR appears more frequently in both clinical and academic settings. This case highlights potential alternative methods to diagnose amyloidosis using tendon, rather than the gold standard of cardiac biopsy or fat pad. This may be less invasive and easier to access, thereby serving as a viable proxy in the future.

Source: Pelter M, Aziz M, Keller RM. Hands stained with Congo red: diagnosing ATTR amyloid in a patient with longstanding heart failure with reduced ejection fraction and new carpal tunnel syndrome. Presented at: American College of Cardiology 70th Annual Scientific Session, May 15-17, 2021.

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