Familial progressive cardiac conduction defect (PCCD)
is a cardiac (heart) conduction disorder that may progress to complete heart block. Affected people may not have any symptoms, or the condition may cause shortness of breath, dizziness, fainting, abdominal pain, heart failure, or sudden death. Mutations in several genes, including the SCN5A, SCN1B and TRPM4 genes, can cause PCCD. Several other genes may be the cause when PCCD occurs with congenital heart disease. Familial PCCD is usually inherited in an autosomal dominant manner. However, not all people that have the mutated gene will have the condition; in those that do, symptoms and severity can vary (known as reduced penetrance and variable expressivity). Autosomal recessive inheritance and sporadic cases have been reported, but are rare. Treatment includes implantation of a pacemaker. Source: Genetic and Rare Diseases Information Center (GARD), supported by ORDR-NCATS and NHGRI.