We have improved the "polymerase chain reaction" (PCR) to permit rapid analysis of any known mutation in genomic DNA. We demonstrate a system, ARMS (Amplification Refractory Mutation System), that allows genotyping solely by inspection of reaction mixtures after agarose gel electrophoresis. The system is simple, reliable and non-isotopic. It will clearly distinguish heterozygotes at a locus from homozygotes for either allele. The system requires neither restriction enzyme digestion, allele-specific oligonucleotides as conventionally applied, nor the sequence analysis of PCR products. The basis of the invention is that unexpectedly, oligonucleotides with a mismatched 3'-residue will not function as primers in the PCR under appropriate conditions. We have analysed DNA from patients with alpha 1-antitrypsin (AAT) deficiency, from carriers of the disease and from normal individuals. Our findings are in complete agreement with allele assignments derived by direct sequencing of PCR products.

BackgroundNiemann-Pick disease type C (NP-C) is a rare neurovisceral lipid storage disorder characterised by progressive, disabling neurological symptoms and premature death in most patients. During the last decade, national cohort studies have accrued a great deal of data on the symptomatology and natural history of NP-C.MethodsIn an observational cohort study, we present a substantial update based on the clinical presentation and follow-up of all known UK-based patients with a confirmed diagnosis of NP-C who have been tracked on an electronic database at the Department of Genetic Medicine, University of Manchester, UK. Patients were stratified according to accepted age-at-neurological-onset categories. Data on patients’ clinical signs and symptoms, medical history and genetic studies are summarised using descriptive methods.ResultsA total of 146 patients with NP-C were included, representing the full known UK NP-C cohort, as observed from database information between 1999 and the end of 2011: 72 patients (49 %) were alive at the end of the observation period. Among a total of 116 patients (79 %) who possessed at least one identified, disease-causing NP-C gene mutation, 114 (98 %) had NPC1 and two (2 %) had NPC2 mutations. Overall, 53/194 (27 %) identified mutations were novel. Six patients (4 %) had an early, non-neurological neonatal onset form of NP-C. The numbers (%) of patients with accepted age-at-neurological onset forms were: 8 (5 %) early-infantile onset, 51 (35 %) late-infantile onset, 42 (29 %) juvenile onset, and 25 (17 %) adolescent/adult onset. Fourteen patients diagnosed based on visceral symptoms and/or sibling history, confirmed in most cases by genetic analysis, did not have any neurological manifestations at last follow up (11 patients with mean [SD] age at last follow up 2.5 [1.8] years: 3 with mean [SD] age at death 20.8 [15.9] years). A total of 51 patients (35 %) received miglustat therapy. The mean (SD) overall treatment duration up to the end of the observation period was 2.6 (2.3) years.ConclusionsThis UK cohort is the largest national NP-C cohort reported to date, and confirms the wide phenotypic variability of the disease, as reported in other countries. Further analyses are required to assess the impact of miglustat therapy on neurological disease progression.Electronic supplementary materialThe online version of this article (doi:10.1186/s12883-015-0511-1) contains supplementary material, which is available to authorized users.

Niemann-Pick disease type C (NPC) is an autosomal recessive, neurovisceral lipid storage disorder. Mutations in two genes (NPC1 and NPC2) produce indistinguishable clinical phenotypes by biochemical mechanisms that have not yet been entirely clarified. The wide spectrum of clinical presentations of NPC includes hepatic and pulmonary disease as well as a range of neuropsychiatric disorders. Late-onset disease has been increasingly recognized as the biochemical diagnosis of NPC has been more widely applied in adult neurology clinics. The clinical presentation and follow-up of 94 patients with NPC is described, 58 of whom were still alive at the time this report was prepared. The age at diagnosis ranged from the prenatal period (with hydrops fetalis) up to 51 years. This review of NPC patients in the UK confirms the phenotypic variability of this inherited lipid storage disorder reported elsewhere. Although a non-neuronopathic variant has been described, most patients in this series who survived childhood inevitably suffered neurological and in some cases neuropsychiatric deterioration. While symptomatic treatment, such as anticholinergic and antiepileptic drugs, can alleviate some aspects of the disease, there is a clear need to develop a specific treatment for this progressively debilitating neurodegenerative disorder.

Mutations in the GNPTAB and GNPTG genes cause mucolipidosis (ML) type II, type III alpha/beta, and type III gamma, which are autosomal recessively inherited lysosomal storage disorders. GNPTAB and GNPTG encode the α/β‐precursor and the γ‐subunit of N‐acetylglucosamine (GlcNAc)‐1‐phosphotransferase, respectively, the key enzyme for the generation of mannose 6‐phosphate targeting signals on lysosomal enzymes. Defective GlcNAc‐1‐phosphotransferase results in missorting of lysosomal enzymes and accumulation of non‐degradable macromolecules in lysosomes, strongly impairing cellular function. MLII‐affected patients have coarse facial features, cessation of statural growth and neuromotor development, severe skeletal abnormalities, organomegaly, and cardiorespiratory insufficiency leading to death in early childhood. MLIII alpha/beta and MLIII gamma are attenuated forms of the disease. Since the identification of the GNPTAB and GNPTG genes, 564 individuals affected by MLII or MLIII have been described in the literature. In this report, we provide an overview on 258 and 50 mutations in GNPTAB and GNPTG, respectively, including 58 novel GNPTAB and seven novel GNPTG variants. Comprehensive functional studies of GNPTAB missense mutations did not only gain insights into the composition and function of the GlcNAc‐1‐phosphotransferase, but also helped to define genotype‐phenotype correlations to predict the clinical outcome in patients.