Neurofibromatosis type 1 (NF1) is a common autosomal dominantly inherited, tumour predisposition syndrome affecting 1/3,000-4,000 individuals worldwide. This inherited disorder results from the mutational inactivation of the NF1 gene on human chromosome 17. The NF1 gene contains 61 exons that give rise to 12kb mRNA encoding neurofibromin. The 327kDa (2,818 amino acid) neurofibromin protein is expressed in most tissues and has a number of alternative isoforms. Neurofibromin is a tumour suppressor protein and down-regulates cellular Ras. Increased active Ras-GTP levels also stimulate the important PI3K/AKT/mTOR signalling pathway that protects cells from apoptosis.

The major clinical featues of NF1 include multiple café-au-lait macules, skinfold freckles, iris Lisch nodules, and neurofibromas. The diagnostic criteria for clinical diagnosis have been well established. However, there are a small number of cases in which the diagnosis is not certain. The germline mutation rate for the NF1 gene is 10-fold higher than that observed for most other inherited diseases. Using a combination of different techniques, almost 95% of germline mutations can be detected. To date, only two firm genotype phenotype correlations have been reported. NF1 phenotype exhibits large variations within a family, evidence for modifying loci regulating the expression of an NF1 gene is beginning to emerge. We also are gaining knowledge on the molecular mechanisms associated with the development of different types of tumours. It is encouraging that the results of recent laboratory and clinical research are finally being translated into clinical trials. With the availability of high-throughput technologies, sophisticated animal models, and multi-centre clinical trials, the future for NF1 sufferers is looking optimistic.

This book aims to provide an overview of the genetic and clinical aspects of NF1 and its role in both NF1-associated and sporadic tumour development. It emphasizes the recent developments in this field and some of the promising on-going clinical trials.

Current knowledge of the etiology of congenital malformations of the human gastrointestinal tract is covered in this book, prefaced by some introductory notes on embryological development. Malformations involving the esophagus, stomach, small and large intestine, anus and rectum, pancreas, and hepato-billiary system are covered. There is a focus on covering those malformations for which a molecular genetic etiology is understood, but other causations, including environmental exposures, twinning, and unknown etiology are also included. For completeness, some disorders are included which are not, strictly, malformations, or which do not, strictly, involve the gastrointestinal tract. Such disorders include Hirschsprung disease, congenital diaphragmatic hernia, omphalocele, and gastroschisis. Suggested approaches to clinical evaluation of individuals with gastrointestinal malformations are included.

This book reviews the molecular genetics of the thalassemia syndromes, inherited hemoglobin disorders that comprise the commonest monogenic disorders globally. Thalassemias are found in high frequencies in tropical regions corresponding to the malaria belt. Beta thalassemia traits show high HbA2 by HPLC, and β-globin mutations (commonly point mutations) are detected by using ARMS-PCR, reverse dot-blot analysis and β-globin gene sequencing. Globally >300 β globin gene mutations exist, however regional mutations are limited to 5-6 common ones. Alpha globin gene defects can only be identified by molecular tests, the exception being HbH disease that shows “golf ball” appearance in HbH preparation, pre-integration peaks on HPLC and a fast-moving band on hemoglobin electrophoresis. Multiplex Gap-PCR identifies common α-globin gene deletions. Specific PCR across the junction caused by the unequal crossing over can detect α-gene triplication. However, heterozygosity or homozygous triplication cannot be resolved by this technique. Non-deletional α-thalassemia can be characterized by specific α-globin gene sequencing. Identification of unusual deletions requires Multiplex Ligation-dependent Probe Amplification. In conclusion, the molecular characterization of human globin gene disorders is required to resolve the phenotypically heterogeneous thalassemia syndromes. Molecular analysis is also an important tool to prevent these disorders by offering prenatal screening in regions with a high disease burden.

Osteogenesis imperfecta (OI) is a disease encompassing a group of disorders mainly characterized by bone fragility and is the commonest form of heritable bone fragility. In this book, the clinical presentations with particular emphasis on rare phenotypes associated with OI are discussed together with molecular advances in diagnosis and treatment of OI. There is a broad spectrum of clinical severity in OI, ranging from multiple fractures in utero and perinatal death, to near-normal adult stature and low fracture incidence. Facial dysmorphism has been noted, but is not well described, nor is it an invariable feature. Sillence et al., in 1979, provided the clinical classification, which has been further expanded. Genetic defects in type 1 collagen can be identified in 85% of patients with a clinical diagnosis of OI, that is, mutations in COL1A1/COL1A2, which follows an autosomal dominant pattern of inheritance. Several genes have now been implicated in autosomal recessive forms of OI and X-linked osteoporosis. Given the possible antenatal presentation and prognosis associated with OI, it is important to make this diagnosis early and be able to distinguish this from other lethal skeletal dysplasias. It is also important to distinguish nonaccidental injury from a pathological cause of fractures, such as OI, and diagnose this promptly in these situations. However, this is not always possible due to variability in presentation and inability to pinpoint the precise genetic etiology despite extensive genetic testing. OI is one such rare genetic condition where treatment is available in the form of bisphosphonates, which has a huge impact on quality of life. Despite advances in medical therapy, multidisciplinary management including physiotherapy remains the mainstay of treatment and improved outcomes in OI.