SNP Shot: Genomic Insights

Treacher Collins syndrome is a disorder that impacts the development of facial bones and tissues. The symptoms and severity of this condition are highly variable, ranging from very mild to severe. Typically, individuals affected have underdeveloped cheekbones and a significantly small jaw and chin, a condition called micrognathia. Some also present with a cleft palate, an opening in the roof of the mouth. In the most severe instances, the underdevelopment of facial bones can obstruct an infant's airway, leading to potentially fatal breathing difficulties.

Individuals with Treacher Collins syndrome commonly exhibit downward-slanting eyes, sparse eyelashes, and a notch in the lower eyelid known as an eyelid coloboma. Some may have other eye abnormalities that can impair vision. This condition is further characterized by missing, small, or abnormally shaped ears. Roughly half of those affected experience hearing loss, which results from defects in the middle ear bones that transmit sound or from the incomplete development of the ear canal. Generally, individuals with Treacher Collins syndrome possess normal cognitive abilities.

Inheritance:

Treacher Collins syndrome, when caused by variations in the TCOF1 or POLR1D gene, is classified as an autosomal dominant condition. This means that only one copy of the altered gene in each cell is enough to cause the disorder. Approximately 60% of these cases arise from new gene variations and occur in individuals without any family history of the syndrome. In the remaining autosomal dominant cases, the affected individual inherits the altered gene from a parent who also has Treacher Collins syndrome. When variations in the POLR1C gene cause Treacher Collins syndrome, it follows an autosomal recessive inheritance pattern. This means that both copies of the gene in each cell must have variations for the condition to manifest. In autosomal recessive inheritance, each parent carries one copy of the altered gene, but they typically do not exhibit any symptoms of the condition themselves.