Progressive familial heart block type I. Clinical and pathological observations.

Progressive familial heart block type I (PFHB-I) is an autosomal inherited disease. It was previously postulated that the disease is limited to the cardiac conduction tissue. The presentation of a patient with dilated cardiomyopathy focused on the possibility that this might be part of PFHB-I. This observation led to routine echocardiographic examination of patients with complete heart block, who belonged to PFHB-I families, and another 5 cases with signs of dilated cardiomyopathy were identified. This is the first time, to our knowledge, that the histological picture of PFHB-I has been described. From these case reports it is clear that in the presence of a dilated cardiomyopathy the prognosis in PFHB-I tends to be poor.