Work

AL Cardiac Amyloidosis Presenting as Grade 3 ATTR Mimicry on Scintigraphy

Year: 2026

Type: article

Abstract: BACKGROUND: Grade 2 or 3 uptake on 99mTc-pyrophosphate scintigraphy is a cornerstone for diagnosing transthyretin amyloidosis. However, light-chain amyloidosis can infrequently mimic this pattern, causing diagnostic error. CASE SUMMARY: A 53-year-old man with heart failure presented with left ventricular hypertrophy and elevated biomarkers. Cardiac magnetic resonance suggested infiltration. 99mTc-pyrophosphate scintigraphy showed intense grade 3 (Perugini) uptake. However, immunofixation revealed an immunoglobulin G lambda clone. Fat and duodenal biopsies confirmed systemic light-chain amyloidosis (AL). DISCUSSION: Grade 3 uptake in AL is a rare diagnostic "false flag" signifying heavy infiltration. Hematologic evaluation is mandatory in patients with positive uptake to avoid misclassification. TAKE-HOME MESSAGES: Grade 3 uptake in AL is an infrequent finding indicating advanced myocardial infiltration and poor prognosis. Hematologic screening is mandatory before interpreting scintigraphy to prevent misclassifying severe AL as transthyretin amyloidosis.

Source: JACC Case Reports

DOI: 10.1016/j.jaccas.2025.106595