Heterozygous nonsense SCN5A mutation W822X explains a simultaneous sudden infant death syndrome.

The sudden, unexpected, and unexplained death of both members of a set of healthy twins (simultaneous sudden infant death syndrome (SSIDS)) is defined as a case in which both infants meet the definition of sudden infant death syndrome individually. A search of the world medical literature resulted in only 42 reported cases of SSIDS. We report the case of a pair of identical, male, monozygotic twins, 138 days old, who suddenly died, meeting the full criteria of SSIDS and where a genetic screen was performed, resulting in a heterozygous nonsense SCN5A mutation (W822X) in both twins. Immunohistochemistry was performed on cardiac tissue samples utilizing polyclonal antibodies anti-Na+ CP type Valpha (C-20) and a terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick end labeling assay. The cellular localization of the Na+ CP type Valpha (C-20) demonstrated by confocal microscopy on staining pattern of myocytes was concentrated in the intercalated disks of ventricular myocytes. These findings suggest that defective ion channels represent viable candidates for the pathogenesis of SIDS and, obviously, of SSIDS, supporting a link between sudden infant death syndrome and cardiac channelopathies.