Background: Setleis syndrome (SS) is a focal facial dermal dysplasia presenting with bilateral temporal skin lesions, eyelash abnormalities and absent meibomian glands. SS is a rare autosomal recessive disorder caused by mutations in the TWIST2 gene, which codes for a transcription factor of the bHLH family known to be involved in skin and facial development. Methods: We obtained gene expression profiles by microarray analyses from control and SS patient primary skin fibroblast and lymphoblastoid cell lines. Results: Out of 983 differentially regulated genes in fibroblasts (fold change ≥ 2.0), 479 were down-regulated and 509 were up-regulated, while in lymphoblasts, 1248 genes were down-regulated and 73 up-regulated. RT-PCR reactions confirmed altered expression of selected genes. Conclusions: TWIST2 is described as a repressor, but expression profiling suggests an important role in gene activation as well, as evidenced by the number of genes that are down-regulated, with a much higher proportion of down-regulated genes found in lymphoblastoid cells from an SS patient. As expected, both types of cell types showed dysregulation of cytokine genes. These results identify potential TWIST2 target genes in two important cell types relevant to rare disorders caused by mutations in this bHLH gene.

We present a rare case of focal facial dermal dysplasia type 4 (FFDD4) in an otherwise healthy boy infant, presenting as bilateral preauricular scarlike defects surrounded by a hair collar, resembling membranous aplasia cutis congenita. The presence of a hair collar supports the hypothesis that FFDD is caused by abnormal closure at facial embryonic fusion lines, but unlike midline scalp defects is not associated with neurological compromise. Other types of FFDD occur at different sites and can be associated with cranial dysgraphism. Awareness of this rare condition by dermatologists is imperative to enable prompt recognition and minimize diagnostic delay.

Focal facial dermal dysplasias (FFDDs) are rare genetic/developmental disorders characterised by bilateral \'scar-like\' facial lesions. Four subtypes are classified by the bitemporal (FFDD1-3) or preauricular (FFDD4) lesion location. FFDD1-3 are differentiated by additional facial abnormalities and inheritance patterns. Although the genetic defects causing FFDD1 and FFDD2 remain unknown, recent studies identified defects causing FFDD3 and FFDD4. Here, the clinical phenotypes, genetic defects and inheritance of the four FFDD subtypes are described. In addition, the overlapping facial abnormalities in FFDD3 and two other genetic disorders, Ablepharon macrostomia syndrome and Barber-Say syndrome, are noted. Familiarity with the FFDDs by clinicians will further delineate the phenotypes and genetic/developmental defects of these dermal facial disorders.

Setleis syndrome, focal facial dermal dysplasia type III (FFDD3, MIM #227260), is characterized by scar-like bitemporal lesions and other ocular and facial dysmorphic features. The syndrome results from recessive mutations in the TWIST2 gene, encoding a basic helix-loop-helix transcription factor or de novo genomic duplication or triplication, which include 1.3 Mb at 1p36.22p36.21, or other yet undefined lesions, emphasizing the syndrome\'s genetic heterogeneity. Recently, three patients were reported with 1p36.22p36.21 duplications/triplication that had the characteristic FFDD3 features and developmental delay or intellectual disabilities. Here, we describe a male with this microduplication, and the typical FFDD3 phenotype, but normal intelligence. Notably, his duplication was inherited from his father who did not have any FFDD3 manifestations, indicating lack of penetrance of the 1p36.22p36.21 microduplication. These findings emphasize phenotypic heterogeneity of the 1p36.22p36.21 copy number variant and the importance of screening the parents of patients with the 1p36.22p36.21 copy number variant to determine whether the duplication/triplication is de novo or inherited, for informed reproductive and genetic counseling.

Setleis syndrome is characterized by bitemporal scar-like lesions and other characteristic facial features. It results from recessive mutations that truncate critical functional domains in the basic helix-loop-helix (bHLH) transcription factor, TWIST2, which regulates expression of genes for facial development. To date, only four nonsense or small deletion mutations have been reported. In the current report, the clinical findings in a consanguineous Turkish family were characterized. Three affected siblings had the characteristic features of Setleis syndrome. Homozygosity for the first TWIST2 missense mutation, c.326T>C (p.Leu109Pro), was identified in the patients. In silico analyses predicted that the secondary structure of the mutant protein was sustained, but the empirical force field energy increased to an unfavorable level with the proline substitution (p.Leu109Pro). On a crystallographically generated dimer, p.Leu109 lies near the dimer interface, and the proline substitution is predicted to hinder dimer formation. Therefore, p.Leu109Pro-TWIST2 alters the three dimensional structure and is unable to dimerize, thereby hindering the binding of TWIST2 to its target genes involved in facial development.

BACKGROUND: Focal facial dermal dysplasias are a group of inherited ectodermal disorders characterized by congenital bitemporal or periauricular scar-like depressions as well as other facial and nonfacial developmental defects. Four subtypes have been delineated, and mutations in the TWIST2 gene have been identified in type III focal facial dermal dysplasia (Setleis syndrome).
METHODS: We describe a sporadic patient with the hallmark bitemporal scar-like lesions, severe intellectual disability, and focal epilepsy.
RESULTS: The boy has typical features of Setleis syndrome, and he developed focal epilepsy, a previously unreported feature of this syndrome. No mutations in the TWIST2 gene were found, and there were no pathologic copy number abnormalities.
CONCLUSIONS: Epilepsy could represent a new manifestation, and the patient described broadens the spectrum of clinical features associated with Setleis syndrome, including central nervous system involvement.

The authors report on a child with Setleis syndrome (OMIM 227260). She is born to a consanguineous couple with bitemporal scar like defects resembling forceps marks. She had other classical features resembling autosomal recessive Setleis syndrome. The authors identified a novel homozygous deletion of a single nucleotide (c.91delC) in TWIST2 gene leading to the premature truncation of protein (p.R31GfsX71). Umbilical hernia and genital anomalies are being reported for the first time with this condition. This is the fourth mutation proven family of Setleis syndrome.

Focal facial dermal dysplasia (FFDD) Type IV is a rare syndrome characterized by facial lesions resembling aplasia cutis in a preauricular distribution along the line of fusion of the maxillary and mandibular prominences. To identify the causative gene(s), exome sequencing was performed in a family with two affected siblings. Assuming autosomal recessive inheritance, two novel sequence variants were identified in both siblings in CYP26C1-a duplication of seven base pairs, which was maternally inherited, c.844_851dupCCATGCA, predicting p.Glu284fsX128 and a missense mutation, c.1433G>A, predicting p.Arg478His, that was paternally inherited. The duplication predicted a frameshift mutation that led to a premature stop codon and premature chain termination, whereas the missense mutation was not functional based on its in vitro expression in mammalian cells. The FFDD skin lesions arise along the sites of fusion of the maxillary and mandibular prominences early in facial development, and Cyp26c1 was expressed exactly along the fusion line for these facial prominences in the first branchial arch in mice. Sequencing of four additional, unrelated Type IV FFDD patients and eight Type II or III TWIST2-negative FFDD patients revealed that three of the Type IV patients were homozygous for the duplication, whereas none of the Type II or III patients had CYP26C1 mutations. The seven base pairs duplication was present in 0.3% of healthy controls and 0.3% of patients with other birth defects. These findings suggest that the phenotypic manifestations of FFDD Type IV can be non-penetrant or underascertained. Thus, FFDD Type IV results from the loss of function mutations in CYP26C1.

We report a case of focal preauricular dermal dysplasia in an 18-day-old healthy girl. We discuss the classification of focal preauricular dermal dysplasia within the spectrum of focal facial dermal dysplasia and aplasia cutis congenita.

BACKGROUND: The focal facial dermal dysplasias (FFDDs) are a group of inherited disorders of facial development, characterised by bitemporal or preauricular scar-like defects, the former resembling \'forceps marks\'. Recently, different homozygous TWIST2 nonsense mutations were reported in unrelated Setleis syndrome (FFDD Type III) patients from consanguineous families, consistent with autosomal recessive inheritance. Mexican-Nahua sibs with facial and ophthalmologic features of FFDD type III were evaluated.
METHODS: Genomic DNAs were isolated for sequencing of the TWIST2 gene. The clinical features and inheritance of all previously reported FFDD patients were reviewed.
RESULTS: The affected sibs were homozygous for a novel TWIST2 frameshift mutation, c.168delC (p.S57AfsX45). Notably, both parents and two heterozygous sibs had distichiasis and partial absence of lower eyelashes. The FFDD subtypes were reclassified: the \'Brauer-Setleis\' phenotype (autosomal dominant with variable expressivity) as FFDD type II; and patients with preauricular lesions as a new subtype, FFDD type IV.
CONCLUSIONS: FFDD type III heterozygotes with TWIST2 mutations may have syndromic manifestations. Review of previous FFDD patients resulted in reclassification of the subtypes.