Ghent University Faculty of Medicine and Health Sciences Department of Internal Medicine Nephrology Division Screening for Fabry disease indications, methods and implications Wim Terryn Thesis submitted in fulfilment of the requirements for the degree of Doctor in Medical Sciences 2013 Promotors: prof. dr. Raymond Vanholder prof. dr. Bruce Poppe Faculteit Geneeskunde en Gezondheidswetenschappen Departement Interne Geneeskunde Divisie Nefrologie Screening voor de Ziekte van Fabry indicaties, methoden en implicaties Wim Terryn Proefschrift voorgelegd tot het behalen van de graad van Doctor in de Medische Wetenschappen 2013 Promotoren: prof. dr. Raymond Vanholder prof. dr. Bruce Poppe Promotors Prof. dr. Raymond Vanholder Ghent University, Faculty of Medicine and Health Sciences Department of Internal Medicine, Nephrology Division Prof. dr. Bruce Poppe Ghent University, Faculty of Medicine and Health Sciences Center for Medical Genetics Members of the examination committee Prof. dr. Elfriede Debaere Universiteit Gent, België Prof. dr. Linda De Meirleir Vrije Universiteit Brussel, België Prof. dr. Olivier Devuyst Universität Zürich, Switserland Dr. Gabor Linthorst Universiteit van Amsterdam, Nederland Prof. dr. Koen Pameleire Universiteit Gent, België Prof. dr. Rudy Van Coster Universiteit Gent, België Prof. dr. Koen Vandewoude Universiteit Gent, België © Wim Terryn Screening for Fabry disease: indications, methods and implications / W. Terryn Universiteit Gent, Campus UZ Gent, De Pintelaan 185, 9000 Gent Thesis Universiteit Gent 2013 – with summary in Dutch and French Lay-out, cover & figures: Dirk De Weerdt (www.ddwdesign.be) General Table of Contents Chapter 1 7 The Place of Fabry Disease among the Sphingolipidoses and Inborn Errors of Metabolism Chapter 2 49 Screening for Fabry Disease in High-Risk Populations Chapter 3 85 Attenuated Fabry Disease Chapter 4 99 Screening and Treatment in Chronic Kidney Disease Chapter 5 123 General Discussion and Perspectives Appendix: Population Screening: Problems associated with the detection of atypical or unknown variants and presentation of a possible solution 131 Summary 137 Samenvatting 141 Résumé 145 Curriculum Vitae 149 Woorden van dank 153 6 Chapter 1 1 The Place of Fabry Disease among the Sphingolipidoses and Inborn Errors of Metabolism Chapter 1: Contents Preface 9 Introduction 11 Metabolism 11 Inborn errors of metabolism: from black urine to gene alterations 11 The lysosome is the stomach of the cell 13 In lysosomal storage disorders, an enzyme deficiency causes storage of intermediary degradation products 14 The clinical presentation of LSDs is extremely variable 16 Sphingolipidoses are lysosomal storage disorders caused by accumulation of sphingolipid degradation products 17 Fabry disease: Case Study 27 A short review on Fabry disease 28 Epidemiology 29 Clinical description 29 Determination of enzyme activity is the gold standard for diagnosis of Fabry disease in males 34 In females, mutation analysis should confirm a clinical suspicion of Fabry disease 34 Mutation detection and mutation scanning 36 Fabry disease has a wide phenotypical spectrum, a low genotype-phenotype correlation and is difficult to recognize 37 Conventional medical treatment of Fabry disease 37 Enzyme replacement therapy in Fabry disease 38 Case study: Discussion 38 Conclusion 39 Aims and Outlines of this thesis 40 References 42 Fabry disease among the sphingolipidosis and inborn errors of metabolism PREFACE abry disease is a rare X-linked progressive multisystem disorder that belongs to the group of lysosomal storage disorders (LSDs). Signs and symptoms of Fabry disease Fmay be first noted in childhood, such as acroparesthesia, heat intolerance, the in- ability to sweat and micro-albuminuria. However, because physicians often do not attribute these signs and symptoms to Fabry disease, patients may not be diagnosed until adulthood, when cerebrovascular disease, cardiac hypertrophy and progressive kidney disease can oc- cur. Fabry disease manifests itself not only in males but also in heterozygotes. Heterozy- gous females show a more variable and in general a more attenuated course. Nonetheless, the mean life expectancy is significantly shortened in both sexes albeit more prominent in males than in females. The name “Fabry disease” originates from the 19th century. In Fabry patients, angiokera- tomas, which are small purplish skin lesions, progressively appear on the skin and were first described in 1898 by two independently working physicians, William Anderson and Johannes Fabry (Figure 1.1.) 1. Figure 1.1. Johannes Fabry. “Ein beitrag zur Kenntniss der Purpura haemorrhagica nodularis” (Purpura papulosa haemorrhagica Hebrae) 1898. 9 Chapter 1 In the late 1950s and early 1960s, de Duve and colleagues identified the lysosome as a cellular organelle responsible for intracellular digestion and recycling of macromolecules. This was the scientific breakthrough that would lead to the understanding of the physiolog- ical basis of the LSDs. Pompe disease was the first disease to be identified as a LSDs in 1963 2.The deficiency of α-Galactosidase was first shown to be the enzymatic defect in Fabry disease in 1967 by Brady and colleagues using radiolabelled globotriaosylceramide (Gb-3), which is accumulated in Fabry disease 3. Subsequently, Kint from the Ghent University dem- onstrated that α-Galactosidase could act on the synthetic substrates (p-nitrophenyl–α-d- galactoside and 4-methylumbelliferyl–α-d-galactoside) and was specific for the α-anomeric galactosidic linkage 4. This breakthrough eventually facilitated the diagnosis of Fabry dis- ease. 10 Fabry disease among the sphingolipidosis and inborn errors of metabolism INTRODUCTION n inborn errors of metabolism (IEMs), a defect in a protein that functions as enzyme, co- factor or transport protein leads to the accumulation or the deficiency of a metabolite. IMost of these deficiencies concern one single protein. They can be classified according to the general type of metabolism or the specific cellular organelle that is involved. Classes of IEMs concern the metabolism of amino acids, organic acids, carbohydrates, fatty acids, metals, or are due to deficiencies in lysosomal or peroxisomal enzymes. Most IEMs are very rare, but as a group, they are common. The symptoms of IEMS are extremely diverse, and can be almost any presenting complaint, especially in children, ranging from growth failure and skin rashes to immunodeficiency, vomiting and hyperventilation. Owing primarily to advances in diagnostic technology, a rapidly growing list of IEM presenting in adulthood is emerging. Some of these, e.g. Scheie disease, are caused by are milder variants of the same enzyme deficiency that commonly causes death in childhood. Others, such as clas- sical hemochromatosis, almost never present in childhood. Fabry disease belongs to the sphingolipidoses, which are a group of LSDs, where a defective activity of a lysosomal pro- tein results in intra-lysosomal accumulation of undegraded metabolites. In the first part of this chapter, a short introduction to the IEMs is presented with more details on the sphingolipidoses. Metabolism In all cells of living organisms, a set of chemical reactions, called “metabolism” enables growth, reproduction, maintenance of structure, and response to the environment. The term metabolism is derived from the Greek “μεταβολη”, which means “change”: a chemi- cal reaction takes place where substance 1 is being transformed into substance 2, because substance 1 has to be degraded or because substance 2 has to be generated. In multicel- lular organisms, enzymes mediate a significant number of these chemical reactions. These are large biological molecules that catalyse or increase the rate of the chemical reaction. In case of IEMs, changes in the genes that encode for an enzyme disable the chemical reac- tion, resulting either in the accumulation of substance 1 or in a deficiency of substance 2. (Figure 1.2.) Inborn errors of metabolism: from black urine to gene alterations Alkaptonuria or “black urine disease” is a key example of how IEMs shaped our current understanding of these rare diseases 5. It was the first IEM described in 1902 by Sir Archibald Garod. This disease was much later fully described as the result of a defect in the hepatic en- zyme homogentisate 1,2 –deoxygenase (encoded by the HGD gene) which participates in the degradation of the amino-acid tyrosine. As a result, a toxic tyrosine degradation product 11 Chapter 1 Figure 1.2. Inborn errors of metabolism: a mutation in the gene that codes for an enzyme results in the accu- mulation of substance 1 or the deficiency of substance 2. homogentisic acid or alkapton accumulates and is excreted in the urine in large quantities. This causes damage to cartilage (resulting in osteoarthritis, especially causing low back pain at young age) and heart valves and precipitates as kidney stones. Homogentisic acid, when exposed to air, colours black staining the sclera and urine of these patients. Since 1902, hundreds of IEM have been described and can be classified according to the concerning defective metabolic pathway or cellular organelle , Presentation is usually in the neonatal period but can occur at any time, even in adult- hood. In older children and adolescents, an IEM should be considered in case of subtle neurologic or psychiatric abnormalities. Many of these patients who have been diagnosed with “birth injury”, atypical psychiatric disorders or medical diseases like multiple sclerosis,