Treacher Collins syndrome has mutations in TCOF1, POLR1C, and POLR1D genes. Clinical features include long upper lip and philtrum, elongated face, slender digits, hypothyroidism, immune dysfunction, hearing loss, pulmonary atresia, ventricular septal defects (VSDs), and hypoplastic pulmonary arteries. Velocardiofacial syndrome is a 22q11 deletion syndrome or TBX1 gene resulting in abnormalities in heart, parathyroid, thymus, and facial development. Clinical features include flat midface, epicanthal folds, retinal detachments, cataracts, joint hypermobility, and sensorineural hearing loss, in addition to the typical signs of PRS. It is an autosomal dominant condition defined as a mutation of COL genes, affecting collagen formation. In one study, 47% of syndromic PRS patients were diagnosed with Stickler syndrome. Stickler syndrome is the most common syndrome associated with PRS. There have been 34 syndromes associated with syndromic PRS, the most common being Stickler syndrome. Alternatively, syndromic PRS has been recently reported to account for 60% of PRS. Some evidence suggests SOX9 or KCNJ2 mutations (on chromosome 17) may affect the development of facial structures and cartilage development, leading to PRS. Non-syndromic PRS has been associated with mutations on chromosomes 2, 4, 11, or 17. The etiology of PRS is typically separated into isolated and syndromic PRS.
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