Familial cartilage-hair hypoplasia: prenatal ultrasound features and clinical outcomes in three siblings with identical RMRP variants.

Clonal Hematopoiesis in Cartilage-Hair Hypoplasia

Cartilage-hair hypoplasia (CHH) is an autosomal recessive syndromic immunodeficiency with skeletal dysplasia, short stature, hypotrichosis, variable degree of immune dysfunction and increased incidence of anaemia, Hirschsprung disease and malignancy. CHH is caused by variants in the RMRP gene, encoding the untranslated RNA molecule of the mitochondrial RNA-processing endoribonuclease, which participates in for example cell cycle regulation and telomere maintenance. Recent studies have expanded our understanding of the complex pathogenesis of CHH. Immune dysfunction has a major impact on clinical course and prognosis. Clinical features of immune dysfunction are highly variable, progressive and include infections, lung disease, immune dysregulation and malignancy. Mortality is increased compared with the general population, due to infections, malignancy and pulmonary disease. Several risk factors for early mortality have been reported in the Finnish CHH cohort and can be used to guide management. Newborn screening for severe combined immunodeficiency can possibly be of prognostic value in CHH. Regular follow-up by a multidisciplinary team should be implemented to address immune dysfunction in all patients with CHH, also in asymptomatic cases. Haematopoietic stem cell transplantation can cure immune dysfunction, but its benefits in mildly symptomatic patients with CHH remain debatable. Further research is needed to understand the mechanisms behind the variability of clinical features, to search for potential molecular treatment targets, to examine and validate risk factors for early mortality outside the Finnish CHH cohort and to develop management guidelines. This review focuses on the pathogenesis, clinical course and management of CHH.

Cartilage-hair hypoplasia (CHH) is a rare syndromic inborn error of immunity, caused by variants in the noncoding RNA gene RMRP. The effects of RMRP deficiency are pleiotropic, affecting the ribosomal RNA processing, cell cycle, and gene regulation. Typical clinical manifestations of CHH include chondrodysplasia with short stature, hair hypoplasia, combined immunodeficiency, and anemia. In addition, individuals with CHH have increased prevalence of malignancies, Hirschsprung’s disease, and autoimmunity. The only curative option for immunodeficiency or severe anemia in CHH remains hematopoietic stem cell transplantation. This review summarizes 60 years of CHH research, covering genetic aspects, pathogenesis, clinical and laboratory features, as well as diagnostic and management considerations in CHH.

Cartilage-hair hypoplasia is a rare autosomal recessive skeletal dysplasia. It is particularly prevalent in the Finnish and Amish populations but increasing reports have been documented worldwide. It is caused by pathogenic variants in the RMRP gene. The clinical presentation is highly variable and may include short-limbed short stature, metaphyseal abnormalities, hypotrichosis, and immune deficiency, among other features. Some of the manifestations may present early in the prenatal period and ultrasound assessment is often the tool that raises suspicion for this condition. This review aims to summarize the current knowledge regarding the prenatal diagnosis of cartilage-hair hypoplasia, focusing on its molecular basis and the role of imaging and genetic testing. A comprehensive literature search was conducted in the PubMed/MEDLINE database using the terms 'Prenatal diagnosis', 'Cartilage-hair hypoplasia', 'Skeletal dysplasias', 'Osteochondrodysplasias' and 'RMRP mutation'. Prenatal diagnosis of this condition remains challenging, as ultrasound findings may overlap with other skeletal dysplasias, including lethal forms. Lethality predictors and the potential of molecular testing are also explored. A structured prenatal approach, combined with timely genetic counselling, may allow for an earlier diagnosis and support informed reproductive decisions. Given the recent advances in reproductive technologies and the potential impact of cartilage-hair hypoplasia on affected individuals, this condition should be actively considered in future studies addressing the prenatal diagnosis of skeletal dysplasias.

Cartilage-hair hypoplasia (CHH) is an autosomal recessive disorder resulting in short stature and hypoplasia of hair. Associated features include impaired T-cell-mediated immunity, deficient erythropoiesis, gastrointestinal dysfunction, and an increased risk of malignancies. As the condition may, in some cases, be severe or even fatal during childhood, families with a previous history of CHH may wish to have prenatal diagnosis. We have previously assigned the gene for CHH to the proximal 9p by linkage analysis using several polymorphic DNA markers. Here we report the prenatal testing for CHH in three Finnish and one Australian family using three DNA markers closely linked to the CHH gene. In three cases a fetus unaffected with CHH was predicted at the probability level of more than 94 per cent. In one case, an affected fetus was predicted. The results were in concordance with ultrasonography performed for all fetuses. The three children born to date were unaffected as predicted. The DNA marker-based analysis thus provides a useful method for early prenatal testing for CHH.

Cartilage‑hair hypoplasia (CHH) is an autosomal recessive form of metaphyseal chondrodysplasia caused by RNA component of mitochondrial RNA processing endoribonuclease (RMRP) gene variants; however, its molecular etiology remains unclear. Whole‑exome sequencing was performed to detect possible pathogenic variants in a patient with a typical short stature and sparse hair. A co‑segregation analysis was also conducted and variants in the family members of the patient were confirmed by Sanger sequencing. A novel compound heterozygous variant in RMRP (NR_003051.4: n.‑21_‑2dup and n.197C>T) was identified in the affected patient. Data from 2 years and 4 months of follow‑up showed a positive effect of growth hormone (GH) therapy on height. Subsequently, two gene expression profiles associated with CHH were obtained from the EMBL‑EBI ENA and ArrayExpress databases. Differentially expressed genes between patients with CHH and healthy controls were selected using R software and were subjected to core analysis using ingenuity pathway analysis (IPA) software. IPA core analysis showed that the 'cell cycle checkpoints' was the most prominent canonical pathway, and the top enriched diseases and functions included various types of cancer, immunological diseases, development disorders and respiratory diseases. The integrative analysis displayed that RMRP can regulate the aberrant expression of downstream targets mainly via the transcription factor TP53, which results in the inhibition of 'cell cycle checkpoints'; eventually, functions associated with the CHH phenotype, such as 'growth failure or short stature' are activated. In conclusion, novel disease‑causing genetic variants of RMRP expand the genetic etiology of CHH, which must be clinically differentiated from achondroplasia. The findings of the present study provide new insights into the mechanisms underlying CHH.

Reduced Intensity Conditioning In Children Undergoing Unrelated Umbilical Cord Blood Transplantation for Non-Malignant Diseases: Preliminary Results Demonstrate a High Rate of Engraftment and Low Incidence of Gvhd

Biallelic pathogenic variants in RMRP, the gene encoding the RNA component of RNase mitochondrial RNA processing enzyme complex, have been reported in individuals with cartilage hair hypoplasia (CHH). CHH is prevalent in Finnish and Amish populations due to a founder pathogenic variant, n.71A > G. Based on the manifestations in the Finnish and Amish individuals, the hallmarks of CHH are prenatal-onset growth failure, metaphyseal dysplasia, hair hypoplasia, immunodeficiency, and other extraskeletal manifestations. Herein, we report six Japanese individuals with CHH from four families. All probands presented with moderate short stature with mild metaphyseal dysplasia or brachydactyly. One of them had hair hypoplasia and the other immunodeficiency. By contrast, the affected siblings of two families showed only mild short stature. We also reviewed all previously reported 13 Japanese individuals. No n.71A > G allele was detected. The proportions of Japanese versus Finnish individuals were 0% versus 70% for birth length < -2.0 SD, 84% versus 100% for metaphyseal dysplasia and 26% versus 88% for hair hypoplasia. Milder manifestations in the Japanese individuals may be related to the difference of genotypes. The mildest form of CHH phenotypes is mild short stature without overt skeletal alteration or extraskeletal manifestation and can be termed "RMRP-related short stature".

Cartilage hair hypoplasia syndrome (OMIM # 250250) is a rare autosomal recessive metaphyseal dysplasia, characterized by disproportionate short stature, hair hypoplasia and variable extra-skeletal manifestations, including immunodeficiency, anemia, intestinal diseases and predisposition to cancers. Cartilage hair hypoplasia syndrome has a broad phenotype and it is caused by homozygous or compound heterozygous mutation in the mitochondrial RNA-processing endoribonuclease on chromosome 9p13. Although it is well known as a primordial dwarfism, descriptions of the prenatal growth are missing. To add further details to the knowledge of the phenotypic spectrum of the disease, we report on two siblings with cartilage hair hypoplasia syndrome, presenting n.64C > T homozygous mutation in the mitochondrial RNA-processing endoribonuclease gene. We describe the prenatal and postnatal growth pattern of the two affected patients, showing severe pre- and post-natal growth deficiency.

Context: Cartilage-hair hypoplasia is a rare hereditary cause of short stature. The aim of this study was to familiarize physicians with this rare but important disease. Evidence Acquisition: This article is a narrative review of the scientific literature to inform about clinical features and management of Cartilage-hair hypoplasia. A systematic search identified 127 papers include original and review articles and case reports. Results: Cartilage-Hair Hypoplasia characterized by short-limb dwarfism associated with metaphyseal chondrodysplasia. The inheritance is autosomal recessive. Other findings include hair hypoplasia, anemia, immunodeficiency, propensity to infections, gastrointestinal disorders (Hirschsprung disease, anal stenosis, esophageal atresia and malabsorption), defective spermatogenesis, increased risk of malignancies and higher rate of mortality. Immunodeficiency in cartilage-hair hypoplasia may be an isolated B-cell or isolated T-cell immunodeficiency or combined B and T-cell immunodeficiency; however, severe combined immunodeficiency is rare. There is no known treatment for hair hypoplasia. Growth hormone was used with conflicting results for short stature in children with Cartilagehair hypoplasia. Skeletal problems must be managed with physiotherapy and appropriate orthopedic interventions. Hirschsprung disease, anal stenosis and esophageal atresia should be surgically corrected. Patients with severe hypoplastic anemia require repeated transfusions. Bone marrow transplantation may be required for patients with severe combined immunodeficiency or severe persistent hypoplastic anemia. Treatment with G-CSF is useful for neutropenia. Patients should be monitored closely for developing malignancy such as skin neoplasms, lymphomas and leukemias. Conclusions: Cartilage-hair hypoplasia is an important hereditary disease with different medical aspects. The high rate of consanguineous marriages in Iran necessitates considering CHH in any child with severe short stature or other clinical features of disorder.

Cartilage-hair hypoplasia (CHH) syndrome is a rare autosomal recessive syndrome associated with skeletal dysplasia, varying degrees of combined immunodeficiency (CID), short stature, hair hypoplasia, macrocytic anemia, increased risk of malignancies, and Hirschsprung disease. To provide clinical and immunological insights obtained from 2 unrelated patients who displayed clinical characteristics of CHH. Two patients with suspected CHH syndrome due to skeletal dysplasia and immunodeficiency underwent an immunological and genetic work-up using flow cytometry, next-generation sequencing (NGS) of the immune repertoire, and Sanger sequencing to identify the underlying defects. Patient 1 presented with low birth weight and skeletal dysplasia. Newborn screening was suggestive of T-cell immunodeficiency, as T-cell receptor excision circle levels were undetectable. Both the T-cell receptor (TCR) Vß and TCR-g (TRG) repertoires were restricted, with evidence of clonal expansion. Genetic analysis identified compound heterozygous RMRP variants inherited from both parents. Patient 2 presented with recurrent lung and gastrointestinal infections, skeletal dysplasia, failure to thrive, and hepatomegaly. The polyclonal pattern of the TCRß repertoire was normal, with only slight overexpression of TCR-ßV20 and restricted expression of Vßs. TRG expressed a normal diverse repertoire, similar to that of the healthy control sample. Genetic analysis identified biallelic novel regulatory variants in RMRP. Both parents are carriers of this mutation. Our findings demonstrate how the immunological work-up, supported by genetic findings, can dramatically change treatment and future outcome in patients with the same clinical syndrome.

Cartilage-hair hypoplasia (CHH) is an autosomal recessive disorder characterized by short stature, hypoplastic hair and humoral immunity disorders. It is a mutation in the RMRP gene, located on chromosome 9p13.3, that leads to CHH. There is no special treatment for short stature in CHH. The efficacy and safety of recombinant human growth hormone (rhGH) therapy in CHH is still under discussion. The present study describes the case of a girl with CHH who was treated with rhGH. The rhGH treatment had a significant effect on the height gain: the height SD score was changed from -4. to -2.98 after 4 years 7 months of treatment. rhGH therapy should be considered as a treatment modality for CHH, and insulin-like growth factor (IGF)-1 and IGF-binding protein 3 concentrations should be closely monitored, particularly because of the increased cancer risk that is a characteristic feature of CHH.

Natural history and genetic spectrum of the Turkish metaphyseal dysplasia cohort, including rare types caused by biallelic COL10A1, COL2A1, and LBR variants.

Cartilage-hair hypoplasia (CHH) is an autosomal recessive metaphyseal chondrodysplasia characterized by short stature and hypoplasia of the hair. Associated pleiotropic features include deficient erythrogenesis, impaired T-cell mediated immunity, Hirschsprung's disease, and an increased risk of malignancies. CHH is most prevalent among the Old Order Amish in the United States and among the Finns, but sporadic families have been described among many other populations. We have previously mapped the gene for CHH to the short arm of chromosome 9 in Finnish and Amish families. The CHH locus resides close to D9S163 within an interval of 1.5 cM flanked by D9S165 and D9S50. In order to investigate the genetic homogeneity of CHH in various populations, we studied nine families with no genealogical connections to either Amish or Finns. No recombinants were detected between the CHH gene and any of the three closest marker loci studied, suggesting that CHH in these families results from mutation(s) at the same locus as in the Amish and Finnish families.

Introduction: Cartilage–hair hypoplasia (CHH) is a rare skeletal dysplasia that presents with various degrees of immunodeficiency, short stature, and a susceptibility to malignancies. Individuals with CHH can present with severe combined immunodeficiency or combined immunodeficiency and are at risk for severe and unusual infections irrespective of their laboratory findings. In addition, individuals with CHH can present with variable skeletal abnormalities, mainly involving the metaphysis of long bones. CHH is a rare disease and familiarity with the variable features is crucial for diagnosis. Methods: We report the clinical, radiological, and genetic findings for 5 patients with proven diagnoses of CHH. Results: In this study we describe a cohort of patients with CHH and present their clinical findings and progressions. In addition, we present the radiological images and the immunological investigations that were done in these patients. Although all the patients in our cohort had poor cellular immunity, they had a variable clinical course. Three out of 5 patients received a bone marrow transplant (BMT) and 2 out of 5 died at an early age (1 after BMT). Those who had poor humoral function had a worse prognosis compared with those with good humoral function. The skeletal findings were characteristic for CHH. Conclusion: CHH is a disease with a variable presentation. Clinicians should be aware of the characteristic skeletal and immunological findings to identify the disease as early as possible. Statement of novelty: We present novel clinical and radiological findings in patients with variable RMRP gene mutations.