An atrial septal defect, secundum (ASDS) is an abnormally large opening in the atrial septum at the site of the foramen ovale and the ostium secundum. ASDS with various cardiac and noncardiac defects is a rare disorder identified by Megarbane in 1999. Patients with this disease present with ASDS in association with other rare conditions, such as different heart defects, conduction abnormalities, and noncardiac malformations along the midline of the upper half of the body.
Genetic locus for the disease has not been identified to date. A study has shown a lack of linkage of the disease to the CSX gene (Cardiac-Specific Homeobox), as well as to the chromosomal region 9q13, both of which have been implicated in atrial septal defects and familial heart blocks. Neither has linkage been found to any of the HLA haplotypes.
Megarbane et al., (1999) reported a Lebanese Christian family, in which 13 of the 18 individuals analyzed (9 males and 4 females) were affected with the disease