 Consequently, autopsy-negative sudden cardiac deaths (no physical abnormalities identified) may comprise a larger part of the channelopathies than previously anticipated.Heritable connective tissue diseases are rare, each disorder estimated at one to ten per 100,000, of which Marfan syndrome is the most common.It is carried by the FBN1 gene on chromosome 15, which encodes the connective protein fibrillin-1, inherited as a dominant trait.