Craniorachischisis in a partially trisomic 11 fetus in a family with reproductive failure and a reciprocal translocation, t(6p plus;11q minus).

A familial reciprocal translocation t(6p+;11q−) is presented, unbalanced (6p+) in the craniorachischisic propositus and balanced in his phenotypically normal father, associated with relative infertility, multiple spontaneous abortions, and failure to produce normal offspring. The karyotype-phenotype relationship is discussed with reference to other published cases of partial trisomy for the distal portion of the long arm of chromosome 11, and the concept of deletionunmasking is briefly considered. The occurrence of major neural groove closure defects due to a variety of translocations in mice is noted. The gametic segregation of balanced and unbalanced karyotypes is unique to each particular translocation making recurrence risk projections hazardous in the absence of prior experience with the particular translocation. The questions of the relative importance of genetic inheritance, chromosomal abnormalities, and many environmental factors including possible specific teratogens in causing neural groove closure anomalies are still unsettled. The paucity of published chromosome studies in these malformations is noted. We urge that cytogenetic studies with banding techniques be undertaken on these cases and their parents in order to expand basic knowledge of the role of chromosomal errors in their aetiology.