Treacher Collins syndrome (TCS) is a rare congenital craniofacial disorder with variable penetrance and high genetic and phenotypic heterogeneity. It is caused by pathogenic variants in the TCOF1, POLR1D, POLR1C, and POLR1B genes, and its major characteristic features are malar and mandibular hypoplasia, downward slanting of the palpebral fissures, and conductive hearing loss. In this study, five patients (two males and three females, age range from 2 to 29 years) with TCS were tested by Next-Generation Sequencing (NGS)-based sequencing and clinically characterized. Genetic analyses detected two deletions and one insertion in the TCOF1 gene and one missense variant in the POLR1D gene. Two novel mutations, c.1371_1372insT (p.Lys458*) in the TCOF1 gene and c.295 G>C (p.Gly99Arg) in the POLR1D gene, were identified. Moreover, two already known mutations, c.4369_4373del (p.Lys1457Glufs*12) and c.2103_2106del (p.Ser701Argfs*9) in the TCOF1 gene, were detected. The novel TCOF1 c.1371_1372insT mutation was associated with mild craniofacial manifestations and very rare symptoms of TCS, i.e., developmental delay and moderate intellectual disability. Although incomplete penetrance is a known phenomenon in TCS, surprisingly, the majority of our patients inherited the disease-causing variants from an asymptomatic mother. The unique feature of our study is the observation of causative mutation transmission between asymptomatic family members. Our results expanded the clinical and mutational spectrum of TCS and further confirmed the inter- and intra-familial variability of this disorder.

Összefoglaló. A Treacher Collins-szindróma a mandibulofacialis dysostosisok csoportjába tartozó kórkép. Főbb jellegzetességei a maxillaris és mandibularis dysostosis, az antimongoloid szemrések, az alsó szemhéj colobomája, illetve a vezetéses halláscsökkenés. A szindrómával járó tünetek egyénenként és családon belül is nagyon eltérőek lehetnek; legenyhébb formái csaknem észrevehetetlenek, míg a súlyosabb esetekben az életet veszélyeztető légúti szövődmények léphetnek fel. Hátterében az esetek döntő többségében a TCOF1-gén eltérései játszanak szerepet, mely eltérések autoszomális domináns módon öröklődnek. Esetbemutatásunk célja, hogy felhívjuk a figyelmet a genetikai vizsgálat elvégzésének fontosságára olyan, klinikailag jól felismerhető tünetegyüttes, mint a Treacher Collins-szindróma esetén. Bár a betegség a klinikai kép alapján diagnosztizálható, az ismétlődés kockázatát csak úgy tudjuk pontosan meghatározni, ha ismerjük a családtagok genotípusát. A bemutatott család több tagjánál kimutatható volt a TCOF1-gén mutációja, annak ellenére, hogy klinikai tünetük nem volt. A jelenség magyarázata az inkomplett penetrancia, azaz a hibás gén fenotípusosan nem kerül kifejeződésre. Orv Hetil. 2020; 161(52): 2201–2205. Summary. Treacher Collins syndrome belongs to the group of mandibulofacial dysostoses. Its main features are maxillary and mandibular dysostosis, downward-slanting palpebral fissures, coloboma of the lower eyelid and conductive hearing loss. The symptoms associated with the syndrome can vary greatly from individual to individual and within the family. In its mildest form, the syndrome is almost imperceptible, and when severe, life-threatening respiratory complication can occur. TCOF1 is the major gene involved with an autosomal dominant mode of inheritance. The purpose of our case study is to draw attention to the importance of performing genetic testing in a clinically recognizable disorder such as Treacher Collins syndrome. Although the disease can be diagnosed based on the clinical symptoms, the risk of recurrence can only be accurately determined if the genotype of the family members is known. Several members of the presented family had a mutation in the TCOF1 gene despite having no clinical symptoms. The explanation for this phenomenon is incomplete penetrance, i.e., the defective gene is not expressed in the phenotype. Orv Hetil. 2020; 161(52): 2201–2205.

Noonan syndrome is a relatively common genetic syndrome with clinical and genetic heterogeneity. Besides the characteristic features such as short stature, typical facial features, congenital heart defects, skeletal and ocular anomalies, various orodental manifestations occur with variable frequency. High-arched palate, malocclusions, micrognathism, giant cell lesions, and anomalous lateral incisors are frequently observed features, whereas supernumerary teeth, hypodontia, macrodontia, enamel hypoplasia, severe dental caries, impacted teeth, delayed eruption, taurodontism and odontoma have occasionally been reported. Here, we present a family with three affected members displaying variable dental manifestations carrying the same PTPN11 c.178G>A pathogenic variant. A 14-year-old and a 12-year-old, both female patients, presented high-arched palates, delayed dental eruption and caries. Moreover, the younger sibling exhibited frequently observed manifestations such as malocclusion and gingivitis, and further rare features like open-bite, micrognathia, and crowded teeth were present. The mother of the patients had periodontitis and enamel problems. Monitoring the oral health of the patients with NS is important, as they are prone to severe dental caries, gingival and other orodental problems. Therefore, initiating early orodental examination is highly recommended for patients with suspicion or diagnosis of NS.

Complex chromosomal rearrangements (CCRs) are rare structural abnormalities involving at least three chromosomal breakpoints and often two or more chromosomes. Owing to their inherent genomic complexity, CCRs are frequently associated with abnormal phenotypes, including developmental delay, congenital anomalies, and infertility. In this study, we report four male patients, three of them with de novo rare structural chromosomal rearrangement detected through a combination of Giemsa-Trypsin (GTG) banding, fluorescence in situ hybridization (FISH), and high-resolution microarray techniques (SNP array and array CGH). Each of the four cases turned out to be of a different type: in addition to two exceptional CCRs, an inv dup del 18q and a cluster rearrangement involving the long arm of chromosome 4 were identified. Despite the limitations of the testing methods, we performed a detailed analysis of the relationship between the most detailed genotype data and the associated phenotype. Our study provides further valuable evidence that the use of molecular cytogenetic methods is of paramount importance even in cases with abnormal karyotypes detected by light microscopy, as high-resolution data may reveal unsuspected genomic complexity, which is essential for genetic counseling in these patients.

Heterozygous mutations in the FOXP1 gene (OMIM#605515) are responsible for a well-characterized neurodevelopmental syndrome known as “intellectual developmental disorder with language impairment with or without autistic features” (OMIM#613670) or FOXP1 syndrome for short. The main features of the condition are global developmental delay/intellectual disability; speech impairment in all individuals, regardless of their level of cognitive abilities; behavioral abnormalities; congenital anomalies, including subtle dysmorphic features; and strabismus, brain, cardiac, and urogenital abnormalities. Here, we present two siblings with a de novo heterozygous FOXP1 variant, namely, a four-year-old boy and 14-month-old girl. Both children have significantly delayed early psychomotor development, hypotonia, and very similar, slightly dysmorphic facial features. A lack of expressive speech was the leading symptom in the case of the four-year-old boy. We performed whole-exome sequencing on the male patient, which identified a pathogenic heterozygous c.1541G>A (p.Arg514His) FOXP1 mutation. His sister’s targeted mutation analysis also showed the same heterozygous FOXP1 variant. Segregation analysis revealed the de novo origin of the mutation, suggesting the presence of parental gonadal mosaicism. To the best of our knowledge, this is the first report of gonadal mosaicism in FOXP1-related neurodevelopmental disorders in the medical literature.

Epilepsy represents a highly prevalent neurological disorder with a significant genetic component, particularly implicating ion channel genes, including SCN1A . In this study, 431 individuals with heterogeneous paediatric-onset epilepsy phenotypes were assessed at the Department of Medical Genetics, University of Pécs between 2018 and 2024. Genetic investigations employed Sanger sequencing, targeted epilepsy gene panels, whole exome sequencing, and multiplex ligation-dependent probe amplification for SCN1A copy number analysis. Thirty-six pathogenic or likely pathogenic SCN1A variants were identified, including 15 variants which have not been reported previously. Furthermore, 9 novel variants were detected in 12 additional epilepsy-associated genes. Diagnostic yield was proportional to the breadth of genomic interrogation. WES analysis revealed 6 novel variants in 19 genes. These findings underscore the considerable genetic heterogeneity of epilepsy and demonstrate the clinical utility of gene panels and WES, particularly in complex phenotypes. The identification of novel variants enhances molecular understanding and facilitates more precise genotype-phenotype correlations, reinforcing the value of comprehensive genomic diagnostics in epilepsy management.