Fine-grained facial phenotype–genotype analysis in Wolf–Hirschhorn syndrome

Wolf–Hirschhorn syndrome is caused by anomalies of the short arm of chromosome 4. About 55% of cases are due to de novo terminal deletions, 40% from unbalanced translocations and 5% from other abnormalities. The facial phenotype is characterized by hypertelorism, protruding eyes, prominent glabella, broad nasal bridge and short philtrum. We used dense surface modelling and pattern recognition techniques to delineate the milder facial phenotype of individuals with a small terminal deletion (breakpoint within 4p16.3) compared to those with a large deletion (breakpoint more proximal than 4p16.3). Further, fine-grained facial analysis of several individuals with an atypical genotype and/or phenotype suggests that multiple genes contiguously contribute to the characteristic Wolf–Hirschhorn syndrome facial phenotype.