Two extraordinarily severe cases of Treacher Collins syndrome
AMERICAN JOURNAL OF MEDICAL GENETICS PART A
Authors: Bauer, Mislen; Saldarriaga, Wilmar; Wolfe, S. Anthony; Beckwith, J. Bruce; Frias, Jaime L.; Cohen, M. Michael, Jr.
Abstract
Here, we report two extraordinarily severe cases of Teacher Collins syndrome. Initially, amniotic bands and plical fold disruption were considered, but downslanting eyes made us consider severe Treacher Collins syndrome. A TCOF1 mutation in exon 24 was identified in Patient 1 (c.4355_4356ins14, resulting in p.1456Thrfs*18). Patient 2, who expired on day 4, is so similar to Patient 1 that severe Treacher Collins syndrome may be inferred in this instance. Neither the TCOF1 mutation nor the well-known variability in the expression in affected families with Treacher Collins syndrome (approximate to 40% of reported cases) can explain the severity of these cases; otherwise, we would be aware of such cases within families from time to time. We are unaware of any recent sporadic cases (approximate to 60% of reported cases) exactly like ours either with a single exception in the case reported by Writzl et al. [2008] with a TCOF1 mutation. The case described by Otto in 1841 is spectacular. We propose several hypotheses to be considered in explaining this developmental amplification, including some promoter effect on the gene, some position effect on the gene, a polymorphism elsewhere in the gene, a point mutation elsewhere in the gene, a polymorphism in another gene, or a point mutation in another gene, such as POLR1C (which maps to 6p21.1) or POLR1D (which maps to13q12.2). We also review the etiology and pathogenesis of Treacher Collins syndrome, and discuss several other severe cases from the past. (c) 2013 Wiley Periodicals, Inc.
A Synonymous Mutation in TCOF1 Causes Treacher Collins Syndrome Due to Mis-Splicing of a Constitutive Exon
AMERICAN JOURNAL OF MEDICAL GENETICS PART A
Authors: Macaya, D.; Katsanis, S. H.; Hefferon, T. W.; Audlin, S.; Mendelsohn, N. J.; Roggenbuck, J.; Cutting, G. R.
Abstract
Interpretation of the pathogenicity of sequence alterations in disease-associated genes is challenging. This is especially true for novel alterations that lack obvious functional consequences. We report here on a patient with Treacher Collins syndrome (TCS) found to carry a previously reported mutation, c.122C > T, which predicts p.A41V, and a novel synonymous mutation, c.3612A > C. Pedigree analysis showed that the c.122C > T mutation segregated with normal phenotypes in multiple family members while the c.3612A > C was de novo in the patient. Analysis of TCOF1 RNA in lymphocytes showed a transcript missing exon 22. These results show that TCS in the patient is due to haploinsufficiency of TCOF1 caused by the synonymous de novo c.3612A > C mutation. This study highlights the importance of clinical and pedigree evaluation in the interpretation of known and novel sequence alterations. (C) 2009 Wiley-Liss, Inc.