This congenital heart defect is almost always sporadic, but occasional families in which multiple persons have isolated ASD suggest that a single 'major' gene may sometimes be responsible. The family reported by Zuckerman et al. (1962) suggests dominant ... This congenital heart defect is almost always sporadic, but occasional families in which multiple persons have isolated ASD suggest that a single 'major' gene may sometimes be responsible. The family reported by Zuckerman et al. (1962) suggests dominant inheritance. Zetterqvist (1960) reported a family with 8 proved cases and 5 probable cases of ASD of secundum type in 3 generations. Johansson and Sievers (1967) found 6 proved and 1 probable case of ASD in 3 generations. Furthermore, they were able to show that Zetterqvist's and their cases traced their ancestry to a common couple who lived in the 18th century. Zetterqvist et al. (1971) gave a full report on the family which they felt provided strong evidence for the existence of a single major gene as a determining factor. Sanchez-Cascos (1972) examined 109 cases of ASD, 84 of the ostium secundum type and 25 of the ostium primum type; of these, 92 presented ASD as an isolated defect and 17 were associated with other malformations. He concluded, from the incidence of familial aggregation among first-degree relatives of affected cases, from the fact that the sex ratio deviated from 1 for his cases (0.64 males per 1 female), and from other findings, that multifactorial inheritance is consistent with the demonstrated pattern of transmission. He also reported significant dermatoglyphic findings in these ASD cases--a high proportion of whorls and a parallel diminution in the number of ulnar loops. Lynch et al. (1978) restudied a large kindred reported by Zuckerman et al. (1962) and concluded that 2 autosomal dominant forms of ASD occur: one with (108900) and one without prolongation of the PR interval. Li Volti et al. (1991) observed 3 Sicilian families in which 17 persons (10 females and 7 males) had atrial septal defect of the ostium secundum type without conduction defects. There were several instances of male-to-male transmission.