Genetic homogeneity of cartilage-hair hypoplasia

Cartilage-hair Hypoplasia Complicated with Liver Cirrhosis Due to Chronic Intrahepatic Cholestasis

We herein report a rare case of cartilage-hair hypoplasia (CHH) complicated with liver cirrhosis. A 20-year-old Japanese man with CHH was found incidentally to have liver cirrhosis and an esophageal varix. This patient had been treated for infections due to immunodeficiency since early childhood. He ultimately died of liver failure at 31 years of age. An autopsy revealed an abnormality of the interlobular bile ducts and intrahepatic cholestasis. Liver cirrhosis was thought to have been caused by chronic intrahepatic cholestasis due to biliary duct hypoplasia and changes in the intestinal microbiome. Therefore, CHH may cause biliary cirrhosis due to multiple effects.

Cartilage hair hypoplasia: characteristics and orthopaedic manifestations

PURPOSE

Cartilage hair hypoplasia (CHH) is a rare metaphyseal chondrodysplasia characterized by short stature and short limbs, found primarily in Amish and Finnish populations. Cartilage hair hypoplasia is caused by mutations in the RMRP gene located on chromosome 9p13.3. The disorder has several characteristic orthopaedic manifestations, including joint laxity, limited elbow extension, ankle varus, and genu varum. Immunodeficiency is of concern in most cases. Although patients exhibit orthopaedic problems, the orthopaedic literature on CHH patients is scant at best. The objective of this study was to characterize the orthopaedic manifestations of CHH based on the authors' unique access to the largest collection of CHH patients ever reported.

METHODS

The authors examined charts and/or radiographs in 135 cases of CHH. We analyzed the orthopaedic manifestations to better characterize and further understand the orthopaedic surgeon's role in this disorder. In addition to describing the clinical characteristics, we report on our surgical experience in caring for CHH patients.

RESULTS

Genu varum, with or without knee pain, is the most common reason a patient with CHH will seek orthopaedic consultation. Of the cases reviewed, 32 patients had undergone surgery, most commonly to correct genu varum.

CONCLUSION

This paper characterizes the orthopaedic manifestations of CHH. Characterizing this condition in the orthopaedic literature will likely assist orthopaedic surgeons in establishing a correct diagnosis and appreciating the orthopaedic manifestations. It is important that the accompanying medical conditions are appreciated and evaluated.

Hypoplastic anemia in cartilage-hair hypoplasia-balancing between iron overload and chelation

OBJECTIVE

To evaluate the severity of iron overload and the success of iron chelation therapy in patients with cartilage-hair hypoplasia (CHH) and hypoplastic anemia, with particular focus on adverse effects of iron chelators.

STUDY DESIGN

Four of the 23 presently surviving Finnish patients with CHH under 18 years of age are dependent on regular red blood cell transfusions. Their hospital records were reviewed for history of anemia and chelation therapy. Cumulative iron load from transfusions was calculated. Efficacy of the chelation therapy was evaluated biochemically and by liver iron content assessments.

RESULTS

At the introduction of iron chelation, the patients had received on average 99 (37-151) transfusions; the mean cumulative iron overload was 4640 (800-8200) mg, the annual iron accumulation rate 0.35 (0.25-0.41) mg/kg/d, and the mean plasma ferritin was 2896 (1217-6240) μg/L. Liver iron content, determined by biopsy in 3 patients, was on average 20.0 (6.6-30.0) mg/g liver dry weight. All patients, except 1 with Hirschsprung disease, tolerated deferoxamine, deferiprone, and deferasirox therapy well, showing only mild adverse effects typical for the agents. Plasma ferritin levels and liver magnetic resonance imaging T2* of iron overload showed successful chelation.

CONCLUSION

Iron chelation is well tolerated in patients with CHH, with possible exception of patients with Hirschsprung disease. Successful chelation will prepare for hematopoietic stem cell transplantation in patients with CHH with persistent transfusion dependency.

Mechanisms of Disordered Granulopoiesis in Congenital Neutropenia

Neutrophils are critical components of the innate immune response, and persistent neutropenia is associated with a marked susceptibility to infection. There are a number of inherited clinical syndromes in which neutropenia is a prominent feature. A study of these rare disorders has provided insight into the mechanisms regulating normal neutrophil homeostasis. Tremendous progress has been made at defining the genetic basis of these disorders. Herein, progress in understanding the genetic basis and molecular mechanisms of these disorders is discussed. We have focused our discussion on inherited disorders in which neutropenia is the sole or major hematopoietic defect.

Consequences of mutations in the non-coding RMRP RNA in cartilage-hair hypoplasia

Cartilage-hair hypoplasia (CHH), also known as metaphyseal chondrodysplasia McKusick type (OMIM no. 250250), is an autosomal recessive, multi-systemic disease characterized by disproportionate short stature, fine and sparse hair, deficient cellular immunity and a predisposition to malignancy. It is caused by mutations in RMRP, the RNA component of the ribonucleoprotein complex RNase MRP, and, thus, CHH represents one of few Mendelian disorders caused by mutations in a nuclear encoded, non-coding RNA. While studies in yeast indicate that RMRP contributes to diverse cellular functions, the pathogenesis of the human condition is unknown. Studies of our CHH patient cohort revealed mutations in both the promoter and the transcribed region of RMRP. While mutations in the promoter abolished transcription in vitro, RMRP RNA levels in patients with transcribed mutations were also decreased suggesting an unstable RNA. RMRP mutations introduced into the yeast ortholog, NME1, exhibited normal mitochondrial function, chromosomal segregation and cell cycle progression, while a CHH fibroblast cell line exhibited normal mitochondrial content. However, the most commonly found mutation in CHH patients, 70A>G, caused an alteration in ribosomal processing by altering the ratio of the short versus the long form of the 5.8S rRNA in yeast. Transcriptional profiling of CHH patient RNAs showed upregulation of several cytokines and cell cycle regulatory genes, one of which has been implicated in chondrocyte hypertrophy. These data suggest that alteration of ribosomal processing in CHH is associated with altered cytokine signalling and cell cycle progression in terminally differentiating cells in the lymphocytic and chondrocytic cell lineages.

The Finnish Disease Heritage III: the individual diseases

This article is the third and last in a series entitled The Finnish Disease Heritage I-III. All the 36 rare hereditary diseases belonging to this entity are described for clinical and molecular genetic purposes, based on the Finnish experience gathered over a period of half a century. In addition, five other diseases are mentioned. They may be included in the list of the "Finnish diseases" after adequate complementary studies.

The association of Buschke-Ollendorf syndrome and nail-patella syndrome

Buschke-Ollendorf syndrome and nail-patella syndrome are both rare connective tissue disorders inherited in an autosomal dominant pattern and characterized by cutaneous and bone lesions. We describe a 3-year-old boy and his family who showed clinical features of both Buschke-Ollendorf syndrome and nail-patella syndrome. To our knowledge, this association has not been reported previously, suggesting that these two connective tissue disorders may share the same gene location with different mutations or involve different mutated genes that share downstream segments of their signaling pathways. Furthermore, this young patient is also affected by a chronic idiopathic neutropenia usually not observed in Buschke-Ollendorf syndrome or nail-patella syndrome.

Mutations in the RNA component of RNase MRP cause a pleiotropic human disease, cartilage-hair hypoplasia

The recessively inherited developmental disorder, cartilage-hair hypoplasia (CHH) is highly pleiotropic with manifestations including short stature, defective cellular immunity, and predisposition to several cancers. The endoribonuclease RNase MRP consists of an RNA molecule bound to several proteins. It has at least two functions, namely, cleavage of RNA in mitochondrial DNA synthesis and nucleolar cleaving of pre-rRNA. We describe numerous mutations in the untranslated RMRP gene that cosegregate with the CHH phenotype. Insertion mutations immediately upstream of the coding sequence silence transcription while mutations in the transcribed region do not. The association of protein subunits with RNA appears unaltered. We conclude that mutations in RMRP cause CHH by disrupting a function of RNase MRP RNA that affects multiple organ systems.

Characterization of the human talin (TLN) gene: genomic structure, chromosomal localization, and expression pattern

Talin is a high-molecular-weight cytoskeletal protein, localized at cell-extracellular matrix associations known as focal contacts. In these regions, talin is thought to link integrin receptors to the actin cytoskeleton. Talin plays a key role in the assembly of actin filaments and in spreading and migration of various cell types. Talin proteins are found in a wide variety of organisms, from slime molds to humans. The human Talin (HGMW-approved symbol TLN) gene was previously mapped to chromosome 9p, but little was known of its sequence and genomic structure. To characterize human TLN further, we have isolated a single bacterial artificial chromosome clone, harboring the entire gene. The gene extends over more than 23 kb and consists of 57 exons. We have localized TLN to human chromosome band 9p13 by both fluorescence in situ hybridization and radiation hybrid mapping. Northern blot analysis detected TLN expression in various human tissues, including leukocytes, lung, placenta, liver, kidney, spleen, thymus, colon, skeletal muscle, and heart. Based on its chromosomal location, expression pattern, and protein function, we considered TLN as a candidate gene for cartilage-hair hypoplasia (CHH), an autosomal recessive metaphyseal chondrodysplasia, previously mapped to 9p13. We sequenced the entire TLN coding sequence in several CHH patients, but no functional mutations were detected.

Bone marrow transplantation in cartilage-hair hypoplasia: correction of the immunodeficiency but not of the chondrodysplasia

We diagnosed cartilage-hair hypoplasia (CHH) in a female child with prenatal-onset short stature, metaphyseal chondrodysplasia, and severe combined immunodeficiency leading to recurrent, severe respiratory tract infections. The patient required several hospital admissions during her 1st year of life and failed to thrive in spite of antimicrobial therapy and hypercaloric nutrition. Bone marrow transplantation (BMT) from an HLA-identical sister was performed at age 16 months after conditioning with busulphan and cyclophosphamide, using 9 x 10(8) nucleated bone marrow cells/kg body weight. Graft-versus-host disease prophylaxis consisted of cyclosporine and methotrexate. The post-transplantation period was uneventful. She developed full and sustained chimerism as demonstrated by DNA analysis of granulocytes and mononucleated cells on days 44, 69 and 455 post BMT. Cellular immunity was completely reconstituted at 4 months, humoral immunity at 15 months post BMT. The patient is alive and well 24 months post BMT without medication, but the radiological osseous changes persist, and longitudinal growth remains markedly below the 10th percentile for CHH standards; her height at age 3 years 4 months is 66 cm.

CONCLUSION

In this patient with unusually severe CHH, bone-marrow transplantation has fully corrected the immune deficiency but has had no influence on the course of the chondrodysplasia.