De novo balanced translocation (6;18)(q21;q21.3 or q22) [corrected] in a patient with heterotaxia.

We report on a sporadic case of heterotaxia with a de novo chromosome structural abnormality. The patient had inversely located heart (dextrocardia), stomach, duodenum, and cecum. In addition, she had cerebral atrophy, hypertelorism with telecanthus, infraorbital skin furrows, ear-lobe grooves, prominent maxilla and teeth, large carp mouth, short fifth fingers with limited flexion, generalized hypotonicity, and severe psychomotor retardation. High-resolution chromosome banding analysis demonstrated an apparently balanced translocation: 46,XX,t(6;18)(q21;q21.3). It is hypothesized that both heterotaxia and the chromosomal abnormality in the patient are causally related and a putative situs determining gene has been disrupted by the chromosome break, i.e., a position effect or a cryptic deletion at around the breakpoints. The translocation in our patient may be a good source for positional cloning of the gene.