SNP Shot: Genomic Insights

Donnai-Barrow syndrome is a genetic condition that affects various areas of the body. Key characteristics include distinct facial features such as widely spaced, downward-sloping eyes; a short, bulbous nose with a flattened bridge; rotated ears; and a prominent widow's peak.

Individuals with this syndrome commonly experience significant hearing impairment due to inner ear abnormalities (sensorineural hearing loss). Vision impairments are also frequent, including severe nearsightedness (high myopia), retinal detachment or degeneration, and progressive vision decline. Some individuals may also exhibit iris coloboma, a gap or split in the iris.

Nearly all individuals with Donnai-Barrow syndrome present with an underdeveloped or absent corpus callosum, the structure connecting the brain's hemispheres. Additional brain structure abnormalities can also occur. Mild to moderate intellectual disability and developmental delays are typical.

Congenital diaphragmatic hernia, a hole in the diaphragm, can also occur in individuals with Donnai-Barrow syndrome. This birth defect allows abdominal organs to migrate into the chest, potentially impacting heart and lung development. An omphalocele, where abdominal organs protrude through the navel, can also be present. Less commonly, individuals with Donnai-Barrow syndrome may have defects in the intestines, heart, or other organs.

Inheritance:

Donnai-Barrow syndrome follows an autosomal recessive inheritance pattern. This means that both copies of the responsible gene must have mutations for the condition to manifest. Parents are typically carriers, each possessing one mutated copy of the gene, but usually show no symptoms. In rare cases, uniparental disomy (UPD) has been observed, where an individual inherits both copies of the mutated gene from one parent (in the case described, the father) and none from the other. UPD is a genetic event that can happen randomly during the formation of egg or sperm cells or during early fetal development.