A group of diverse inherited disorders that arise from deficiency of enzymes required for the breakdown of products of intermediary metabolism.
Diagnosis depends on a high index of suspicion, and is easily made by biochemical test or mutational analysis. Tissue biopsy is rarely required to make the diagnosis.
Many present in early childhood with hepatosplenomegaly, neurodevelopmental delay, cardiorespiratory disease, joint contractures, and failure to thrive. Others present later in childhood with pain, organ enlargement, skin rash, sensory organ damage, musculoskeletal abnormalities, muscle weakness, and neurodevelopmental delay.
Early referral to a specialist center is strongly advised so that patients and families may be assessed by a multidisciplinary team familiar with the disease.
Significant advances in treatment have occurred in recent years such that the outlook for patients has substantially changed. Specific treatments limited to certain subtypes include enzyme replacement therapy, substrate reduction therapy, and stem cell transplantation.
Lysosomal storage diseases (LSDs) are due to the inherited deficiency of one of over 40 lysosomal enzymes, and lead to accumulation of undegraded substrate in a range of organs and tissues.   They are multisystem and progressive disorders. Clinical manifestations are diverse; presentation may be in childhood or in adult life. New treatments, including replacement of the deficient enzyme, are changing the natural history of these diseases.  
Royal Free Hospital
Professor in Haematology
University College London
ABM has received honoraria, travel expenses, and research funding from Shire, Sanofi, and Protalixys. He is also an author of a number of references cited in this monograph.
Departments of Neurology and Pediatrics
NYU School of Medicine
GMP declares that he has no competing interests.
Paediatric Metabolic Unit
Cambridge University Hospitals
UR has received travel grants, honoraria for lectures, and funding for clinical trials from Shire HGT, Genzyme, and Actelion.
Head of Department
University of Mainz
MB has been reimbursed by Shire, the manufacturer of Elaprase and Replagal, for attending several conferences, for running educational programs and for consulting. MB has received honoraria for speaking from Genzyme (the manufacturer of Myozyme, Fabrazyme, Aldurazyme, and Cerezyme) and Actelion (the manufacturer of Zavesca). MB is an author of a number of references cited in this monograph.
Associate Professor of Public Health
Director of Research
Gippsland Medical School
EVV declares that he has no competing interests.
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