Trichorhinophalangeal syndrome type I in monozygotic twins discordant for hip pathology. Report on the morphological evolution of cone-shaped epiphyses and the unusual pattern of skeletal maturation

Late Presentation of Tricho-Rhino-Phalangeal Syndrome (TRPS1 Affected) Associated Hip Pathology

Perthes disease typically presents between the ages of 4 and 9 years and is characterized by unilateral or bilateral avascular necrosis of the femoral head. Clinically it presents with pain and decreased range of motion and has a disease course of up to 5 years. We report the clinical and radiological findings of a female in early adolescence who was referred to pediatric physiotherapy and found to have Perthes-like changes of the hip, on a background of tricho-rhino-phalangeal syndrome type 1 (TRPS1). The patient's first symptoms of hip pain were reported at age 10, but there was no radiographic evidence until 2.5 years later when a diagnosis of Perthe's disease was made. This uniquely late presentation may have been due to the altered skeletal maturation seen in TRPS1, whereby skeletal age lags behind chronological age. This case highlights the importance of identifying relevant past medical history on initial assessment, and having rapid access to radiology and orthopedic support to enable timely diagnosis, as prognosis becomes poorer as age increases. Perthes-like changes should be considered as a differential diagnosis in patients presenting with non-traumatic hip pain, regardless of age of onset.

Recombinant Human Growth Hormone Therapy for Childhood Trichorhinophalangeal Syndrome Type I: A Case Report

Trichorhinophalangeal syndrome type I (TRPS I; MIM 190350) is a rare autosomal dominant disorder of congenital malformations due to variants of the gene TRPS1. We reported on an 11-year-old Chinese boy with TRPS I. He had typical clinical findings, including sparse hair, a bulbous nose, a long philtrum, a thin upper lip, and skeletal abnormalities including cone-shaped epiphyses, shortening of the phalanges, and short stature. Trio whole exome sequencing identified a likely pathogenic heterozygous variant c.1957C > T (p.Q653*) in exon 4 of TRPS1, which has not been previously reported. He had been treated with rhGH therapy at a dose of 0.34 mg/(kg/week) at age 11, and a follow-up was conducted for one year. The rhGH therapy led to an increase in growth with a mean growth velocity of 1.12 cm/month (+1.1 SDS/year), and insulin-like growth factor 1 (IGF-1) concentration increased within normal range in our case. Moreover, we summarize 12 cases with TRPS I, including TRPS1 gene variants, growth hormone (GH) axis evaluation, IGF-1 concentration, and treatment in each analyzed case. Eight cases with TRPS I show a good response to rhGH therapy, and five of them have elevated IGF-1. Classic GH deficiency is not common among patients with TRPS I. The presence or absence of GH deficiency is not an absolute criterion for determining whether rhGH therapy should be used in TRPS I. It proves that rhGH therapy improves height outcomes before puberty in TRPS I in the short term. Effects on final adult height will need a longer follow-up and more adult-height data. The rise in IGF-1 could correlate with an increase in short-term height. Measuring IGF-1 levels is recommended as part of the assessment during the follow-up of patients with TRPS I.

Case report: A novel mutation in TRPS1 identified in a Chinese family with tricho-rhino-phalangeal syndrome I: A therapeutic challenge

Tricho-rhino-phalangeal syndrome (TRPS) is a rare autosomal dominant malformation caused by mutations involving the TRPS1 gene. Patients with TRPS exhibit distinctive craniofacial and skeletal abnormalities. This report presents three intra-familial cases with TRPS1 gene mutations that showed the characteristic features of TRPS. A 13-year-old boy was admitted to Department of Endocrinology for the evaluation of short stature. Physical examination revealed that the boy had thin sparse hair, pear-shaped nose, protruding ears, small jaw and brachydactyly. A survey of his family history indicated that the boy's sister and mother shared the same clinical features. Radiological techniques demonstrated a different degree of skeletal abnormalities in these siblings. Next-generation sequencing and quantitative PCR were performed and showed a novel deletion mutation in exons 3-5 in the three familial cases, confirming the diagnosis of TRPS I. The healthy father did not carry the deletion mutation. Currently, there was no specific therapy for TRPS I; however, genetic consultation may be useful for family planning.

Severe brachydactyly and short stature resulting from a novel pathogenic TRPS1 variant within the GATA DNA-binding domain

Brachydactyly type E, which can be an isolated finding or part of a syndrome in combination with other clinical anomalies, involves metacarpals and metatarsals with or without short phalanges. Herein we report two unrelated Turkish females who presented with brachydactyly type E and vitamin D deficiency in the absence of marked alterations in serum calcium, phosphate, and parathyroid hormone. After excluding disease-causing variants in two candidate genes, PTHLH and PDE4D, we identified different pathogenic variants in TRPS1, the gene mutated in patients with tricho-rhino-phalangeal syndrome (TRPS). In one of the patients, who displayed severe brachydactyly and short stature, we identified a novel heterozygous missense pathogenic variant in exon 6 (c.2783A>G, p.Tyr928Cys), located within the GATA DNA-binding domain. The second patient, who had relatively milder brachydactyly and was of normal height, carried a heterozygous nonsense pathogenic variant in exon 4 (c. 1870C>T, p.Arg624Ter), which has been previously described. Both pathogenic variants segregated in affected family members. The patients additionally showed sparse hair and a bulbous nose, consistent with the clinical features of TRPS. Our findings, in addition to identifying the genetic cause of brachydactyly in two unrelated kindreds, emphasize the role of pathogenic TRPS1 variants in the development of brachydactyly type E and highlight the GATA DNA-binding region of TRPS1 protein with respect to phenotype-genotype correlation.

Mutation analysis of TRPS1 gene including core promoter, 5'UTR, and 3'UTR regulatory sequences with insight into their organization

The TRPS1 protein is a potent regulator of proliferation, differentiation, and apoptosis. The TRPS1 gene aberrations are strongly associated with rare trichorhinophalangeal syndrome (TRPS) development. We have conducted MLPA analysis to capture deletion within the crucial 8q24.1 chromosomal region in combination with mutation analysis of TRPS1 gene including core promoter, 5'UTR, and 3'UTR sequences in nine TRPS patients. Low complexity or extent of untranslated regulatory sequences avoided them from analysis in previous studies. Amplicon based next generation sequencing used in our study bridge over these technical limitations. Finally, we have made extended in silico analysis of TRPS1 gene regulatory sequences organization. Single contiguous deletion and an intragenic deletion intervening several exons were detected. Mutation analysis revealed five TRPS1 gene aberrations (two structural rearrangements, two nonsense mutations, and one missense substitution) reaching the overall detection rate of 78%. Several polymorphic variants were detected within the analysed regulatory sequences but without proposed pathogenic effect. In silico analysis suggested alternative promoter usage and diverse expression effectivity for different TRPS1 transcripts. Haploinsufficiency of TRPS1 gene was responsible for most of the TRPS phenotype. Structure of TRPS1 gene regulatory sequences is indicative of generally low single allele expression and its tight control.

Trichorhinophalangeal syndrome type I: a novel mutation and Perthes-like changes of the hip in a family with 4 cases over 3 generations

The trichorhinophalangeal syndrome is a rare genetic syndrome with characteristic craniofacial and skeletal abnormalities including hip pathology in variable manifestation. We describe hip involvement with Perthes-like changes and a novel mutation of the TRPSI gene in a family with 4 affected individuals. This case series underlines the clinical significance of rare genetic disorders such as TRPS that among other differential diagnoses should be kept in mind when children present with Perthes-like changes of the hip joint.

A novel TRPS1 gene mutation causing trichorhinophalangeal syndrome with growth hormone responsive short stature: a case report and review of the literature

The role of growth hormone (GH) and its therapeutic supplementation in the trichorhinophalangeal syndrome type I (TRPS I) is not well delineated. TRPS I is a rare congenital syndrome, characterized by craniofacial and skeletal malformations including short stature, sparse, thin scalp hair and lateral eyebrows, pear-shaped nose, cone shaped epiphyses and hip dysplasia. It is inherited in an autosomal dominant manner and caused by haploinsufficiency of the TRPS1 gene. We report a family (Mother and 3 of her 4 children) with a novel mutation in the TRPS1 gene. The diagnosis was suspected only after meeting all family members and comparing affected and unaffected siblings since the features of this syndrome might be subtle. The eldest sibling, who had neither GH deficiency nor insensitivity, improved his growth velocity and height SDS after 2 years of treatment with exogenous GH. No change in growth velocity was observed in the untreated siblings during this same period. This report emphasizes the importance of examining all family members when suspecting a genetic syndrome. It also demonstrates the therapeutic effect of GH treatment in TRPS I despite normal GH-IGF1 axis. A review of the literature is included to address whether TRPS I is associated with: a) GH deficiency, b) GH resistance, or c) GH-responsive short stature. More studies are needed before recommending GH treatment for TRPS I but a trial should be considered on an individual basis.

Tricho-rhino-phalangeal syndrome in a 13-year-old girl with chronic renal failure and severe growth retardation

INTRODUCTION

The tricho-rhino-phalangeal syndrome type III (TRPS III) is a rare autosomal dominantly inherited condition. The main clinical features are sparse and slow-growing hair and nails, a pear-shaped nose with a bulbous tip, elongated and flat philtrum, thin upper lip, cone-shaped epiphyses of the phalanges, and short stature. All patients have a point mutation in the TRPS1 gene.

CASE REPORT

In this paper, we present a 13-year-old female with the typical clinical features of TRPS III, extreme growth retardation, severe deformities of both proximal radii resulting in limited extension of the elbows, and chronic renal failure (CRF) in addition. Molecular diagnostics revealed a missense mutation in exon 6 of TRPS1 that she inherited from her father who is also affected with TRPS III, but does not have CRF. In the index patient, the CRF was found to be due to bilateral renal hypodysplasia (RHD).

CONCLUSION

Beside the renal dysplasia, the girl had severe deformities of the proximal radii - findings which have not been reported so far in TRPS III.

Identical but not the same: the value of discordant monozygotic twins in genetic research

Monozygotic (MZ) twins show remarkable resemblance in many aspects of behavior, health, and disease. Until recently, MZ twins were usually called "genetically identical"; however, evidence for genetic and epigenetic differences within rare MZ twin pairs has accumulated. Here, we summarize the literature on MZ twins discordant for Mendelian inherited disorders and chromosomal abnormalities. A systematic literature search for English articles on discordant MZ twin pairs was performed in Web of Science and PubMed. A total number of 2,016 publications were retrieved and reviewed and 439 reports were retained. Discordant MZ twin pairs are informative in respect to variability of phenotypic expression, pathogenetic mechanisms, epigenetics, and post-zygotic mutagenesis and may serve as a model for research on genetic defects. The analysis of single discordant MZ twin pairs may represent an elegant approach to identify genes in inherited disorders.

Partial growth hormone deficiency and changed bone quality and mass in type I trichorhinophalangeal syndrome

The trichorhinophalangeal syndromes (TRPSs) are syndromes due to haploinsufficiency of genes in the chromosome 8q24.12 region. Type I TRPS is characterized by typical facial features including sparse, brittle and fine hair, bulbous nose, and a long philtrum, as well as skeletal abnormalities. Growth retardation is a feature frequently found in these patients, who commonly are of short stature; however, only one case with growth hormone deficiency has been described in a TRPS patient and that patient had type II TRPS. Skeletal morphological abnormalities have been studied, but investigation of bone metabolism and quality in this kind of patients are not available. In this report we describe two cases of type I TRPS with partial growth hormone deficiency and significant bone mass and quality impairment, which was unresponsive to GH treatment.

Uncoupling of chondrocyte differentiation and perichondrial mineralization underlies the skeletal dysplasia in tricho-rhino-phalangeal syndrome

Tricho-rhino-phalangeal syndrome (TRPS) is an autosomal dominant craniofacial and skeletal dysplasia that is caused by mutations involving the TRPS1 gene. Patients with TRPS have short stature, hip abnormalities, cone-shaped epiphyses and premature closure of growth plates reflecting defects in endochondral ossification. The TRPS1 gene encodes for the transcription factor TRPS1 that has been demonstrated to repress transcription in vitro. To elucidate the molecular mechanisms underlying skeletal abnormalities in TRPS, we analyzed Trps1 mutant mice (Trps1DeltaGT mice). Analyses of growth plates demonstrated delayed chondrocyte differentiation and accelerated mineralization of perichondrium in Trps1 mutant mice. These abnormalities were accompanied by increased Runx2 and Ihh expression and increased Indian hedgehog signaling. We demonstrated that Trps1 physically interacts with Runx2 and represses Runx2-mediated trans-activation. Importantly, generation of Trps1(DeltaGT/+);Runx2(+/-) double heterozygous mice rescued the opposite growth plate phenotypes of single mutants, demonstrating the genetic interaction between Trps1 and Runx2 transcription factors. Collectively, these data suggest that skeletal dysplasia in TRPS is caused by dysregulation of chondrocyte and perichondrium development partially due to loss of Trps1 repression of Runx2.

Genotypic and phenotypic spectrum in tricho-rhino-phalangeal syndrome types I and III

Tricho-rhino-phalangeal syndrome (TRPS) is characterized by craniofacial and skeletal abnormalities. Three subtypes have been described: TRPS I, caused by mutations in the 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. To investigate whether TRPS III is caused by TRPS1 mutations and to establish a genotype-phenotype correlation in TRPS, we performed extensive mutation analysis and evaluated the height and degree of brachydactyly in patients with TRPS I or TRPS III. We found 35 different mutations in 44 of 51 unrelated patients. The detection rate (86%) indicates that TRPS1 is the major locus for TRPS I and TRPS III. We did not find any mutation in the parents of sporadic patients or in apparently healthy relatives of familial patients, indicating complete penetrance of TRPS1 mutations. Evaluation of skeletal abnormalities of patients with TRPS1 mutations revealed a wide clinical spectrum. The phenotype was variable in unrelated, age- and sex-matched patients with identical mutations, as well as in families. Four of the five missense mutations alter the GATA DNA-binding zinc finger, and six of the seven unrelated patients with these mutations may be classified as having TRPS III. Our data indicate that TRPS III is at the severe end of the TRPS spectrum and that it is most often caused by a specific class of mutations in the TRPS1 gene.