Nager syndrome (MIM #154400) is the best-known preaxial acrofacial dysostosis, mainly characterized by craniofacial and preaxial limb anomalies. The craniofacial abnormalities mainly consist of downslanting palpebral fissures, malar hypoplasia, micrognathia, external ear anomalies, and cleft palate. The preaxial limb defects are characterized by radial and thumb hypoplasia or aplasia, duplication of thumbs and proximal radioulnar synostosis. Haploinsufficiency of SF3B4 (MIM *605593), which encodes SAP49, a component of the pre-mRNA spliceosomal complex, has recently been identified as the underlying cause of Nager syndrome. In our study, we performed exome sequencing in two and Sanger sequencing of SF3B4 in further ten previously unreported patients with the clinical diagnosis of Nager syndrome, including one familial case. We identified heterozygous SF3B4 mutations in seven out of twelve patients. Four of the seven mutations were shown to be de novo; in three individuals, DNA of both parents was not available. No familial mutations were discovered. Three mutations were nonsense, three were frameshift mutations and one T > C transition destroyed the translation start signal. In three of four SF3B4 negative families, EFTUD2 was analyzed, but no pathogenic variants were identified. Our results indicate that the SF3B4 gene is mutated in about half of the patients with the clinical diagnosis of Nager syndrome and further support genetic heterogeneity for this condition.
BackgroundMutations in EFTUD2 were proven to cause a very distinct mandibulofacial dysostosis type Guion-Almeida (MFDGA, OMIM #610536). Recently, gross deletions and mutations in EFTUD2 were determined to cause syndromic esophageal atresia (EA), as well. We set forth to find further conditions caused by mutations in the EFTUD2 gene (OMIM *603892).Methods and resultsWe performed exome sequencing in two familial cases with clinical features overlapping with MFDGA and EA, but which were previously assumed to represent distinct entities, a syndrome with esophageal atresia, hypoplasia of zygomatic complex, microcephaly, cup-shaped ears, congenital heart defect, and intellectual disability in a mother and her two children [AJMG 143A(11):1135-1142, 2007] and a supposedly autosomal recessive oto-facial syndrome with midline malformations in two sisters [AJMG 132(4):398-401, 2005]. While the analysis of our exome data was in progress, a recent publication made EFTUD2 mutations highly likely in these families. This hypothesis could be confirmed with exome as well as with Sanger sequencing. Also, in three further sporadic patients, clinically overlapping to these two families, de novo mutations within EFTUD2 were identified by Sanger sequencing. Our clinical and molecular workup of the patients discloses a broad phenotypic spectrum, and describes for the first time an instance of germline mosaicism for an EFTUD2 mutation.ConclusionsThe clinical features of the eight patients described here further broaden the phenotypic spectrum caused by EFTUD2 mutations or deletions. We here show, that it not only includes mandibulofacial dysostosis type Guion-Almeida, which should be reclassified as an acrofacial dysostosis because of thumb anomalies (present in 12/35 or 34% of patients) and syndromic esophageal atresia [JMG 49(12). 737-746, 2012], but also the two new syndromes, namely oto-facial syndrome with midline malformations published by Mégarbané et al. [AJMG 132(4): 398-401, 2005] and the syndrome published by Wieczorek et al. [AJMG 143A(11): 1135-1142, 2007] The finding of mild phenotypic features in the mother of one family that could have been overlooked and the possibility of germline mosaicism in apparently healthy parents in the other family should be taken into account when counseling such families.
We present two previously unreported and unrelated female patients, one with the tentative diagnosis of acromegaloid facial appearance (AFA), the other with the tentative diagnosis of hypertrichosis with acromegaloid facial appearance (HAFF) with or without gingival hyperplasia. Main clinical features of HAFF were generalized hypertrichosis terminalis and coarse facial features. In both patients, pregnancy was complicated by polyhydramnios, and both had hyperbilirubinemia and persistent fetal circulation. Development was normal in one patient and slightly delayed in the other. At 13 years, both had round faces with full cheeks, thick scalp hair and eyebrows, a low frontal hairline, hirsutism, hyperextensible joints and deep palmar creases. One of them additionally showed gingival hypertrophy and epicanthus, the other one was macrocephalic at birth and at the age of 13 years and suffered from repeated swelling of the soft tissue. Array analysis excluded a 17q24.2-q24.3 microdeletion, which has been reported in patients with hypertrichosis terminalis with or without gingival hyperplasia. Sequencing of the mutational hotspots of the ABCC9 gene revealed two different de novo missense mutations in the two patients. Recently, identical mutations have been found recurrently in patients with Cantú syndrome. Therefore, we propose that ABCC9 mutations lead to a spectrum of phenotypes formerly known as Cantú syndrome, HAFF and AFA, which may not be clearly distinguishable by clinical criteria, and that all patients with clinical signs belonging to this spectrum should be revisited and offered ABCC9 mutation analysis.
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