Molecular Basis, Diagnosis and Clinical Management Of
Total Page:16
File Type:pdf, Size:1020Kb
cardio_special issue 2013_biomarin:Hrev_master 05/03/13 09.19 Pagina 2 Cardiogenetics 2013; 3(s1):exxxx3(s1):e2 Molecular basis, diagnosis storage of glycosaminoglycans (GAGs), previ- ously called mucopolysaccharides.1 The defi- Correspondence: Rossella Parini, Department of and clinical management of ciency of one of the enzymes participating in Pediatrics, San Gerardo Hospital, Via Pergolesi mucopolysaccharidoses the GAGs degradation pathway causes progres- 33, 20900 Monza, Italy. sive storage in the lysosomes and consequently Tel. +39.039.2333286 - Fax: +39.039.2334364. E-mail: [email protected] Rossella Parini,1 Francesca Bertola,2 in the cells and results in tissues and organs 3 Pierluigi Russo dysfunction. The damage is both direct or by Key words: mucopolysaccharidoses (MPS), heart, 1UOS Malattie Metaboliche Rare, activation of secondary and tertiary pathways heart and MPS, genetics and MPS. 2 Department of Pediatrics, Fondazione among which a role is played by inflammation. The incidence of MPSs as a group is reported Acknowledgments: RP and PR acknowledge MBBM, Azienda Ospedaliera San between 1:25000 and 1:45000.3 At present 11 dif- patients and their families and Drs. Andrea Gerardo, University of Milano-Bicocca; ferent enzyme deficiencies are involved in Imperatori and Lucia Boffi who collaborated in 2Consortium for Human Molecular the clinical cardiological evaluation of MPSs MPSs producing 7 distinct clinical phenotypes1 Genetics, University of Milano-Bicocca; patients. RP thanks Fondazione Pierfranco e (Table 1).4 Depending on the enzyme deficien- 3UO Department of Cardiology, Azienda Luisa Mariani of Milano for providing financial cy, the catabolism of dermatan sulphate, support for clinical assistance to metabolic Ospedaliera San Gerardo, Monza, Italy heparan sulphate, keratan sulphate, chon- patients and Mrs. Vera Marchetti, the secretary of droitin sulphate, or hyaluronan may be the Metabolic Unit, for her very useful help in impaired, singly or in combination. Diagnosis is managing the patients. suspected clinically and then confirmed by bio- Abstract chemical, enzymatic and molecular tests. For all Contributions: RP, PR, manuscript preparation and first draft; FB, first draft of paragraph What the MPSs types prenatal diagnosis is available are mucopolysaccharidoses for the molecular biol- Mucopolysaccharidoses (MPSs) are a group through enzymatic or molecular analysis. ogist?; PR first draft of paragraph What are of hereditary, monogenic disorders caused by In contrast to a recent past when there was mucopolysaccharidoses for the cardiologist?; RP, lysosomal storage of glycosaminoglycans. Their only palliative treatment for these diseases, other paragraphs and references writing. All incidence as a group is between 1:25,000 and now many specific treatments like hematopoi- authors reviewed the first draft and discussed the 1:45,000. At present 11 different enzyme defi- etic stem cell transplantation (HSCT) in containedonly concepts. ciencies are know to be responsible of 7 similar selected cases (severe MPS I) and enzyme Conflict of interests: RP has received honoraria, but distinct diseases. The diagnosis is suspected replacement therapy (ERT) for MPS I, II, and travel grants and/or research grants from Shire 5 clinically but must be confirmed through bio- VI are available. These treatments are able to HGT, Genzyme Corporation Inc. and BioMarin; FB chemical, enzymatic and molecular analysis. improve the clinical course of the diseaseusehas received travel grants from Genzyme Prenatal diagnosis is feasible for each disease. mainly if started early. This brings along the Corporation Inc.; PR has received travel grants The phenotype worsens with age, due to pro- responsibility for the clinician to recognize from BioMarin. gressive storage, and mainly involves mucosal these diseases at the first signs to allow access tissue, upper airways and lungs, bones and to treatment before a severe damage has been Received for publication: 22 October 2012. Revision received: 1 January 2013. joints, central and peripheral nervous system, established. In this respect pilot studies of Accepted for publication: 11 January 2013. heart, liver, eye and ear. Any type of MPSs, is newborn screening are ongoing.6 In recent characterized by a wide variability of phenotype years, availability of specific treatments, gen- This work is licensed under a Creative Commons ranging from a severe fetal-neonatal disease to eral improvement of palliative medical care Attribution NonCommercial 3.0 License (CC BY- an attenuated form diagnosed in adult individu- and improvement of recognition of mild cases NC 3.0). als. Recently new treatments, like hematopoiet- presenting later in life, have produced a grow- ic stem cell transplantation and enzymatic ing number of adult MPSs patients in relative- ©Copyright R. Parini et al., 2013 Licensee PAGEPress, Italy replacement therapy, became available for many ly good conditions who need to be cared after Cardiogenetics 2013; 3(s1):e2 of these disorders entailing the urgency of early by adult services for metabolic diseases. doi:10.4081/cardiogenetics.2013.s1.e2 diagnosis to allow access to therapies. Thanks to Preparing the right setting for successful tran- therapies these patients have a longer life than sition of these patients from pediatric to adult in the past and this implies that also Non-commercialpalliative service is a difficult task that all the centers for treatments, of which the cardiological ones have MPSs in Europe are dealing with. GAGs. The qualitative analysis is then suggest- a prominent part, must be undertaken diligently. ed. Diagnosis is established by enzyme assay in The cardiologist may face, more frequently than cultured fibroblasts, leukocytes or serum. In expected, with the need to diagnose a patient clinical laboratories residual enzyme activity is with MPS who was not recognized by other spe- Diagnosis of not accurately quantified and is thus not a valid cialists. The echocardiographic features of these mucopolysaccharidoses predictor of disease outcome.1 Conclusive diag- patients are typical and may help in the clinical diagnosis. The future probably deserves to these and prenatal diagnosis nosis is performed with molecular analysis con- disorders other new treatments or combination firming results of enzyme activity and allowing therapies, which might further improve progno- Diagnosis of MPSs is suspected clinically on an early prenatal diagnosis. sis of these diseases. the basis of a number of clinical features (red When a patient is diagnosed with a MPS dis- flags; Table 2),1,4,7,8 but it needs a laboratory con- order, genetic counseling is recommended. firmation. Urine GAGs analysis is a preliminary Genetic counseling can provide the family with diagnostic test. There is a risk of false positive information regarding the genetics, inheri- Introduction and negative results which is less frequent if a tance, and recurrence risks for the specific MPS 24 h urine sample is collected and analyzed. condition in their family. The mucopolysaccharidoses (MPSs) are a There are patients with a normal GAGs urine When the mutations in the family are known, group of monogenic disorders due to lysosomal concentration but an abnormal distribution of prenatal diagnosis can be performed by molecu- [page 2] [Cardiogenetics 2013; 3(s1):e2] cardio_special issue 2013_biomarin:Hrev_master 05/03/13 09.19 Pagina 3 Review lar analysis of tissue obtained by chorionic vil- mented in previous studies and present in of 653 amino acids.11 So far, more than 180 lus or amniocytes sampling. Enzymatic assay is homozygous state or in heterozygous state with mutations have been reported in MPS I often performed as well to guarantee the minor a second known severe mutation and when the patients spread along the entire coding and risk of misdiagnosis. If the mutations are not clinical phenotype is established according to splicing regions without appreciable mutation- completely known the prenatal diagnosis may standardized scoring index of severity. al hot spots. The two most common worldwide be performed with the enzymatic assay alone on Mutations resulting in large alterations of gene mutations are the nonsense p.W402X and chorionic villus sampling or amniocytes.1 sequence, as nonsense mutations or frame- p.Q70X associated to severe phenotype and shifts insertion/deletions, are generally identi- much frequent in North Europe. p.G51D and fied in patients affected by the severe form of p.P496R are specific Italian severe mutations the disease. Missense and splicing mutations whereas p.P533R, spread to Mediterranean What are are sometime compatible with some enzymatic countries, is associated to an intermediate- residual activity and then result in a wide range severe phenotype.12 mucopolysaccharidoses of phenotypes spanning the entire spectrum for the molecular biologist? from severe to attenuated.1 Mucopolysaccharidosis type II The updating of mutations identified is (MPS II) All MPSs have an autosomal recessive trans- available on Human Gene Mutation Database (http://www.hgmd.org). IDS gene maps to chromosome Xq28 and mission with the exception of MPS type II encodes for iduronate-2-sulphatase. Patients (Hunter syndrome) that is X-linked.9 Mucopolysaccharidosis type I are hemizygous males or, very rarely, females Most of MPSs genes have been identified and due to autosomal-X chromosomal transloca- cloned in the 90’s.10 Only HSGNAT gene, respon- (MPS I) tion or non-random X-chromosome inactiva-