When familial, an autosomal dominant mode of transmission is noted and wide variability is present. Mildly affected family members are recognized by careful cardiac evaluation and appreciation of the adult phenotype. This may relate to the cryptorchidism and male infertility in affected fathers How the altered gene causes the features of the syndrome is not entirely clear. An alternate explanation is that the fetal branchial arch field is developmentally altered. There may be more than one way that this set of physical findings occurs.
Birth weight is typically normal.
But increased birth weight from edema is common. The pubertal growth spurt may be blunted or absent. In infancy the head appears large with prominent eyes that are not slanted. The eyes appear widely spaced with droopy or thick, hooded eyelids. In adolescence the face becomes more triangular.