Branchiootic Syndrome 2

For a phenotypic description and a discussion of genetic heterogeneity of the branchiootic syndrome, see BOS1 (602588).

Clinical Features

Marres and Cremers (1991) described a kindred in which 20 of 74 persons in 3 generations had external ear anomalies, preauricular sinuses (or cysts), and commissural lip pits, either in combination or separately. The external ear anomaly was relatively minor and was found in 12 persons. Eleven persons had unilateral or bilateral preauricular sinus. Two individuals without sinus or ear pit had a palpable preauricular cyst. Eight persons had one or more commissural lip pits, which had not been noticed before the study.

Although Marres and Cremers (1991) had considered the disorder in their family to be distinct because of the absence of cervical fistulae and renal abnormalities and the presence of commissural lip pits, the report by Kumar et al. (2000) suggested that commissural lip pits may not be a true component of the syndrome; one individual who had not inherited the chromosome segment responsible in other affected members had only lip pits.

Baker (1966) found commissural lip pits in 12% of Caucasoids and 20% of blacks. Congenital preauricular sinuses occurred more frequently in persons with pits than in those without pits.

Mapping

In a large family with BO syndrome, Kumar et al. (1998) excluded linkage to the 8q13 region previously identified in families with BOS1.

Using a genomewide search strategy in the family reported by Marres and Cremers (1991) and Kumar et al. (1998), Kumar et al. (2000) identified genetic linkage, with a maximum lod score of 4.81 at a recombination fraction of zero, between the BO phenotype and the polymorphic marker D1S2757 in the 1q31 region.