Background: Hybrid ¹⁸ F-fluorodeoxyglucose (FDG) positron emission tomography and magnetic resonance imaging may differentiate mature fibrosis or scar from fibrosis associated to active inflammation in patients with Anderson-Fabry disease, even in nonhypertrophic stage. This study was designed to compare the results of positron emission tomography and magnetic resonance cardiac imaging with those of speckle-tracking echocardiography in heterozygous Anderson-Fabry disease females. Methods and Results: Twenty-four heterozygous females carrying α-galactosidase A mutation and without left ventricular hypertrophy underwent cardiac positron emission tomography and magnetic resonance using ¹⁸ F-FDG for glucose uptake and 2-dimensional strain echocardiography. ¹⁸ F-FDG myocardial uptake was quantified by measuring the coefficient of variation (COV) of the standardized uptake value using a 17-segment model. Focal ¹⁸ F-FDG uptake with COV >0.17 was detected in 13 patients, including 2 patients with late gadolinium enhancement at magnetic resonance. COV was 0.30±0.14 in patients with focal ¹⁸ F-FDG uptake and 0.12±0.03 in those without ( P <0.001). Strain echocardiography revealed worse global longitudinal systolic strain in patients with COV >0.17 compared with those with COV ≤0.17 (−18.5±2.7% versus −22.2±1.8%; P =0.024). For predicting COV >0.17, a global longitudinal strain >−19.8% had 77% sensitivity and 91% specificity and a value >2 dysfunctional segments 92% sensitivity and 100% specificity. Conclusions: In females carrying α-galactosidase A mutation, focal ¹⁸ F-FDG uptake represents an early sign of disease-related myocardial damage and is associated with impaired left ventricular longitudinal function. These findings support the hypothesis that inflammation plays an important role in glycosphingolipids storage disorders.