[Pediatric cardiac allograft transplantation: a clinicopathological study of twelve recipient hearts]

Objective: To analyze the morphologic changes and the extent of severity in end-stage heart disease; and to explore the correlation with their clinical features. Methods: Twelve cases of recipients who underwent pediatric cardiac allograft transplantation were collected from May 2022 to November 2023 at the Seventh Medical Center of People's Liberation Army of China General Hospital. Gross pathologic examinations were performed and morphological changes were observed under a light microscope after HE, Masson's trichrome, and reticulin staining. Semi-quantitative analysis of morphologic changes was performed. One case received DMD genetic testing, one received mtDNA variation testing for mitochondriopathy, and 1 received metagenomics next-generation sequencing. Clinical data and related literature were reviewed for comprehensive analysis. Results: There were 12 recipient hearts including 11 dilated cardiomyopathy (DCM) and 1 fulminant myocarditis (FM). The median age of DCM was 12 years (range, 3 to 15 years). DCM showed cardiomyocyte hypertrophy, cardiomyocyte disarray, nuclear morphological changes, interstitial fibrosis and fatty infiltration. One DCM was confirmed as Becker muscular dystrophy by DMD genetic testing. No pathogenic mutations were found in 1 patient that received mtDNA variation testing. H. influenzae was detected in the case of FM. FM showed diffuse and full-thickness inflammatory cell infiltration by large numbers of lymphocytes and plasma cells, scattered eosinophils, and few neutrophils. Conclusions: Cardiac transplantation is an excellent treatment for end-stage heart disease. The morphological features of DCM include cardiomyocyte hypertrophy, nuclear morphological changes, interstitial fibrosis and fatty infiltration. The severity of the lesion is influenced by multiple factors. FM predominantly presents diffuse infiltration of lymphocytes and plasma cells.