Extended Data Fig. 5: Clinicopathological findings in Case 4.

A. Before tricaprin treatment, chest radiography (left) and CMR (middle and right) showed cardiomegaly with 9% of left ventricular ejection fraction. The very thin posterolateral wall was positive for LGE. Endomyocardial biopsy showed massive cardiomyocyte steatosis (data not shown), as previously reported²². B. Tricaprin increased the washout rate of ¹²³I-β-methyl-p-iodophenyl-pentadecanoic acid in both the heart and liver in planar images. C. Comparison of macroscopic (upper and middle) and microscopic (lower) myocardial appearance of autopsied hearts between case 4 (middle) and two controls: a normal heart from an 80-year-old man who died from non-heart-related disease (left) and the heart from a 24-year-old man with primary TGCV (right), not treated with tricaprin⁴⁰. In case 4 (middle panels), epicardial and myocardial lipid deposition was much milder than that in a TGCV patient without tricaprin treatment, which showed a whitish and yellowish myocardium with numerous cardiomyocytes displaying vacuolar degeneration with a vesicular appearance in haematoxylin and eosin staining (right panels). Scale bars in the upper, middle, and lower columns are 2 cm, 1 cm, and 20 μm, respectively. D. Macroscopic appearance of transverse sections of the autopsied heart. Gross image (left) and Masson’s trichrome staining (right) are shown. Severe fibrosis was observed in the posterolateral walls, corresponding to the CMR images obtained before tricaprin treatment was initiated (right, Panel A). Abbreviations: CMR, cardiac magnetic resonance; LGE, late gadolinium enhancement; LVEF, left ventricular ejection fraction; P-TGCV, primary triglyceride deposit cardiomyovasculopathy.