Deletion 6(p25.1) in a child with mild dysmorphic features and absence of major eye malformations: Implications for the location of genes involved in ocular development

The authors describe a young girl with an apparently terminal deletion of chromosome 6 at p25.1 Fluorescence in situ hybridization with a chromosome 6 painting probe (ONCOR), showed that the abnormal chromosome 6 is composed entirely of chromosome 6 material. Analysis of the parents chromosomes with the same paint probe ruled out an inherited structural abnormality. To our knowledge, this case is the smallest terminal deletion of 6p yet reported. The patient is a 4 year, 6 month old female who was 3300g at birth. She has global developmental delay and little intelligible speech. Her weight is at the 25th centile, height at the 50th centile for a 3 1/2-year-old, and head circumference at the 25th centile. The eyes are prominent with shallow orbits. She has mild hyperopia and astigmatism. The philtrum is short and the vermillion border is thin. The midface is hypoplastic and there is dental malocclusion. Some of the common features reported in individuals with larger 6p terminal deletions include mental retardation, microcephaly, eye and ear abnormalities, short neck/excess nuchal skin, and flat broad nasal bridge. Our patient lacks several of the features reported in patients with larger deletions of 6p, including the more severe eye defectsmore » (e.g., anterior segment malformations including Peters and Rieger anomalies) described in individuals with 6p23 or 24 terminal deletions. This patient could be important in mapping the critical region for 6p deletion syndrome and for localizing clinical findings to a specific area of 6p. This case also raises the possibility that the gene(s) on 6p important for ocular growth and development are located proximal to 6p25.1.« less