PRKG1 and Naxos disease: To study the familial cases, initially, two different familial forms of ACM have been studied with mutations in desmosomal genes different from PKP2: Naxos disease [mutation in plakoglobin (PKG)] (Protonotarios et al., 1986; McKoy et al., 2000; Protonotarios and Tsatsopoulou, 2004); and Carvajal-syndrome [desmoplakin (DPK)] (Carvajal-Huerta, 1998; Norgett et al., 2000).