Preface

Rare diseases, also referred to as orphan diseases, are diseases affecting a low percentage of the population compared with common diseases. However, more people suffer from rare diseases than cancer and AIDS combined. About 350 million people worldwide are suffering from rare diseases. It is estimated that there are about 7000–8000 different types of rare diseases/disorders. These diseases are rare in some populations but may be common in others, such as Fanconi anemia, which is more prevalent in some regions due to founder mutations in Ashkenazi Jews, the Roma population of Spain, and black South Africans. Evidence and facts from the accumulated data indicate that rare diseases are quite common.

Genetics-causing diseases are classified as chromosomal abnormalities, single gene defects, multifactorial problems, teratogenic problems, and mitochondrial disorders by their etiology.

Most rare diseases are genetics based. Any abnormality of one of the above four categories could result in rare diseases being phenotypic, including some types of malignancies.

Studies of rare diseases offer exciting opportunities and challenges. Knowledge and experience obtained from these studies not only increase our understanding of the correlations between phenotype and genotype, but also have enlightened other areas, particularly in personalized medicine when translating into therapies.

The aim of this book is to increase awareness and exchange experiences and knowledge from experts in field to reduce the challenges and increase an understanding of the nature of rare diseases. As a result, diagnosis/management and care of those suffering from these diseases will hopefully improve.

This book contains 15 chapters covering epidemiology, pathogenesis, clinical characteristics, classification, diagnosis, and disease monitoring using modern technologies, therapies, prevention techniques, data management, and analysis.

To meet the special needs, nine comprehensive literature review chapters were edited focusing on specific types of rare diseases analyzing the past and present and predicting the future of these types of diseases systemically.

We hope this edition will be a helpful and useful book for those studying rare diseases. Most importantly it will benefit patients and improve their quality of life, as well as help families and society reduce social burdens.

Therefore, we would like to express our special thanks to these experienced authors for their valuable contributions to this work.

We would also like to thank the Author Service Manager Ms. Marijana Francetic for her skillful organizational ability and great effort.

> **Dr. Zhan He Wu, MD, PhD, FFSc (RCPA)** Western Sydney Genome Diagnostics, Western Sydney Genetics Program, The Children's Hospital at Westmead, Affiliated to the University of Sydney, Sydney, NSW, Australia

Section 1 Introduction
