The Clinical and Molecular Spectrum of Trichorhinophalangeal Syndrome Types I and II in a Turkish Cohort Involving 22 Patients

OBJECTIVE

Trichorhinophalangeal syndrome is a rare autosomal dominant disorder characterized by distinctive craniofacial and skeletal abnormalities. This study aimed to delineate the trichorhinophalangeal syndrome phenotype and to compare the clinical and molecular findings between trichorhinophalangeal syndrome types I and II.

MATERIALS AND METHODS

A total of 22 trichorhinophalangeal syndrome patients aged 0.9-45 years from 17 families were enrolled. Nineteen patients were diagnosed with trichorhin ophalangeal syndrome I and 3 with trichorhinophalangeal syndrome II. Genetic analyses were made by TRPS1 sequencing and/or chromosomal microarray analyses.

RESULTS

A novel frameshift variant (c.531_532del), a known missense variant, and whole-gene deletions were the pathogenic TRPS1 variants detected in trichorhinophalangeal syndrome I. Three trichorhinophalangeal syndrome II patients had large deletions with variable breakpoints involving the TRPS1-EXT1 interval. All patients had the typical craniofacial findings of trichorhinophalangeal syndrome such as a pear-shaped nose, long philtrum, and thin upper lip, as well as cone-shaped epiphyses. Sparse hair and eyebrows (20/22), short metacarpals and metatarsals (20/22), and small hands (19/22) were common. While craniofacial and limb abnormalities were similar in trichorhinophalangeal syndrome I and II, 3 of 19 trichorhinophal angeal syndrome I patients had mild, and 2 of 3 trichorhinophalangeal syndrome II patients had severe intellectual disability. Three trichorhinophalangeal syndrome II patients including the patient with the EXT1 deletion beginning from exon 2 had exostoses. In trichorhinophal angeal syndrome II, although microdeletion sizes and facial or skeletal features were not correlated, patients with larger deletions had severe intellectual disability.

CONCLUSION

This study has expanded the existing knowledge on the phenotype-genotype spectrum in trichorhinophalangeal syndrome. We suggest including the EXT1 gene partially in the minimal critical region for trichorhinophalangeal syndrome II.

Trps1 Regulates Development of Craniofacial Skeleton and Is Required for the Initiation of Palatal Shelves Fusion

Trichorhinophalangeal syndrome (TRPS) is an autosomal dominant disorder resulting from heterozygous mutations of the TRPS1 gene. Common craniofacial abnormalities in TRPS patients include micrognathia, hypoplastic zygomatic arch, high-arched palate, and, occasionally, cleft palate. Studies have demonstrated that mice with a heterozygous Trps1 mutation (Trps1^+/− mice) have similar features to patients with TRPS, including high-arched palates. However, mice with a homozygous Trps1 mutation (Trps1^−/− mice) exhibit similar but more severe abnormalities, including cleft palate. Our study aimed to characterize the craniofacial phenotype to understand the role of Trps1 in craniofacial development and gain insight on the cleft palate pathogenesis in Trps1 deficiency. Whole-mount skeletal staining revealed hypoplastic skeletal and cartilaginous elements, steep nasal slope, and missing presphenoid in Trps1^−/− mice. Although several craniofacial skeleton elements were abnormal in Trps1^−/− mice, the Trps1 deficiency did not appear to disrupt cranial vault development. All Trps1^−/− mice presented with cleft palate. Analyses of Trps1 expression during palatogenesis detected Trps1 mRNA and protein in palatal mesenchyme and in specific regions of palatal epithelium, which suggested that Trps1 is involved in palatal fusion. Ex vivo culture experiments demonstrated that Trps1^−/− palatal shelves were unable to initiate the fusion process. On the molecular level, Trps1 deficiency resulted in decreased epithelial expression of proteins involved in palatal fusion, including chondroitin sulfate proteoglycan, transforming growth factor-beta 3, Twist1, and beta-catenin. Mesenchymal expression of chondroitin sulfate proteoglycan expression was unaffected, indicating a cell type-specific mechanism of Trps1 regulation on chondroitin sulfate proteoglycan. In conclusion, we demonstrated that Trps1 is involved in the development of craniofacial skeletal elements and in the initiation of the palatal shelves fusion. Furthermore, our studies uncovered that Trps1 is required for epithelial expression of several proteins involved in the palatal shelves fusion.

Pathogenic copy number variants in patients with congenital hypopituitarism associated with complex phenotypes

OBJECTIVES

The aetiology of congenital hypopituitarism (CH) is unknown in most patients. Rare copy number variants (CNVs) have been implicated as the cause of genetic syndromes with previously unknown aetiology. Our aim was to study the presence of CNVs and their pathogenicity in patients with idiopathic CH associated with complex phenotypes.

DESIGN AND PATIENTS

We selected 39 patients with syndromic CH for array-based comparative genomic hybridization (aCGH). Patients with pathogenic CNVs were also evaluated by whole exome sequencing.

RESULTS

Twenty rare CNVs were detected in 19 patients. Among the identified rare CNVs, six were classified as benign, eleven as variants of uncertain clinical significance (VUS) and four as pathogenic. The three patients with pathogenic CNVs had combined pituitary hormone deficiencies, and the associated complex phenotypes were intellectual disabilities: trichorhinophalangeal type I syndrome (TRPS1) and developmental delay/intellectual disability with cardiac malformation, respectively. Patient one has a de novo 1.6-Mb deletion located at chromosome 3q13.31q13.32, which overlaps with the region of the 3q13.31 deletion syndrome. Patient two has a 10.5-Mb de novo deletion at 8q23.1q24.11, encompassing the TRPS1 gene; his phenotype is compatible with TRPS1. Patient three carries a chromosome translocation t(2p24.3;4q35.1) resulting in two terminal alterations: a 2p25.3p24.3 duplication of 14.7 Mb and a 4-Mb deletion at 4q35.1q35.2.

CONCLUSIONS

Copy number variants explained the phenotype in 8% of patients with hypopituitarism and additional complex phenotypes. This suggests that chromosomal alterations are an important contributor to syndromic hypopituitarism.

Thricho-rhino-phalangeal syndrome and severe osteoporosis: a rare association or a feature? An effective therapeutic approach with biphosphonates

Trichorhinophalangeal syndrome (TRPS) is a rare, autosomal dominant malformation syndrome characterized by hair, craniofacial and skeletal abnormalities, skin laxity, deformation of phalanges and anomalies of pelvis, femurs, and tibias. Three subtypes have been described: TRPS I, caused by mutations in TRPS1 gene on chromosome 8; TRPS II, a microdeletion syndrome affecting the TRPS1 and EXT1 genes; and TRPS III, a form with severe brachydactyly, due to short metacarpals, and severe short stature, but without exostoses. We present the case of a 7-year-old boy, affected by TRPS with a severe osteoporosis and several spontaneous bone fractures, an association described only once in the literature, successfully treated with biphosphonates. Bone mineral density (BMD) at dual-energy X-ray Absorptiometry (DXA) was of 0.331 g/cm(2) at lumbar spine with. He had four spontaneous femoral fractures in a year, and for this reason he was been operated for positioning intramedullary osteosynthesis and orthopedic supports. Due to the severity of the clinical and radiological pattern it was established, after approval of the Ethical Committee, to begin off-label therapy with infusions of neridronate at a dose of 2 mg/kg IV every 3 months. The treatment was, in this patient, effective both in terms of clinical (absence of new fractures) and mineralomethric (+45% BMD ath the lumbar level). We therefore suggest that treatment with biphosponates can be taken in account as a possible therapeutic option in case of bone fragility in patients with TRPSI.

The use of cone beam computed tomography for the assessment of trichorhinophalangeal syndrome, type I - a case report

Trichorhinophalangeal syndrome type I is a rare autosomal dominant disorder characterized by cone-shaped epiphysis, sparse fine hair, pear-shaped nose and variable growth retardation. The typical craniofacial features include thin upper lip, elongated philtrum, large outstanding ears, shortened posterior facial height associated with short mandibular ramus and reduced and superiorly deflected posterior cranial base. This report describes a 17-year-old male patient with trichorhinophalangeal syndrome type I and a detailed description of the craniofacial radiographic findings, including the use of cone beam computed tomography images for determination of the airway and temporomandibular joint discrepancies.