There have been extensive studies on the morphological findings and pathogenesis of ARVC/D [1-3]. However, little attention has been directed toward the ultrastructural features of the disease.

The histopathological features of the cardiomy-ocytes in ARVC/D include loss of myofibrils, cellular hypertrophy or degeneration with dystrophic or py-knotic nuclei, and histochemically proven apoptosis [4-6]. Attention is currently focused on the structure of intercalated discs (IDs) and sarcoplasmic reticu-lum (SR) due to the gene mutations that have been discovered both in the autosomal recessive (Naxos Disease) and dominant forms of ARVC/D. These mutations affect plakoglobin in Naxos disease [7], desmoplakin [8-11],plakophilin-2 [12],desmoglein-2 [13], and the cardiac ryanodine receptor (RyR2) [14]. Moreover, mutations have been found at the regulatory site of the TGF^3 [15]. Overexpression of TGF^3 might explain increased fibrosis and affect cell-cell junction stability in ARVC/D.

ARVC/D has been rarely investigated at the ultrastructural level [16-18]. Therefore, analysis of cardiomyocyte ultrastructure, particularly in en-domyocardial biopsy (EMB) tissue and in sections where cardiomyocytes exhibit normal structure under light microscopy, might identify primary cellular defects. This paper reviews cardiomyocyte structure as analyzed by electron microscopy in EMB samples obtained from adolescents and adult patients with a clinical diagnosis of ARVC/D [19].

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