The prevalence of NPC has undoubtedly been underestimated in the past due to a mixture of factors including confusing terminology, prior lack of specific biochemical or genetic tests, varied pathology, and the many variant clinical manifestations of the disease. Epidemiologic data on NPC are very sparse, although prevalence has been estimated at 1:150,000 live births in Western Europe based on the number of cases identified over a 15-year period in France, Germany and the UK.1 In particular, the prevalence of NPC in early life is probably underestimated, owing to its non-specific presentation and high fatality among infants.
Unlike NPA and NPB, which occur most commonly in people of Ashkenazi Jewish ancestry, NPC is considered to be pan-ethnic as it appears to occur with similar frequency across all populations, regardless of ethnic ancestry. Nevertheless, three genetic isolates have been identified that show a higher than average incidence: people of French Acadian descent in Nova Scotia, people of Hispanic descent in parts of Colorado and New Mexico, and a Bedouin group in Israel all show a degree of ‘founder effect’, i.e., a mutation traceable back to a single ancestor or small number of ancestors2,4
National disease registries are important tools in the proper development of regional health policy/infrastructure and allocation of funding. Large collaborative registries collect vital data on the epidemiology (prevalence), symptomatology, and disease management of rare disorders such as NPC. An international NPC registry project is currently ongoing. It aims to enhance the understanding of the natural history of NPC by collecting data from patients irrespective of their treatment.
A recent survey of patients registered on the US National Niemann–Pick C1 database incorporated the largest population of NPC patients studied to date.5 Data on clinical features and patient health problems in NPC1 were obtained from 87 respondents over a 1-year period. A similar patient review, covering a total of 94 patients (58 still alive) has also been conducted in the UK.3 Database surveys such as these provide an overview of important clinical variables as well as the natural history of NPC
References:
1. Patterson MC, Vanier MT, Suzuki K et al. Niemann–Pick disease, type C: a lipid trafficking disorder. In: Scriver CR, Beaudet AL, Sly WS, Valle D, Childs B, Vogelstein B (eds) The Metabolic and Molecular Bases of Inherited Disease, 8th ed, 2001. New York: McGraw-Hill, Ch 145, pp 3611–33.
2. Patterson MC. Niemann–Pick disease Type C. Gene Reviews 2007a (updated 9 July). Accessible at: www.geneclinics.org Accessed 28th May 2009.
3. Imrie J, Dasgupta S, Besley GT et al. The natural history of Niemann–Pick disease type C in the UK. J Inherit Metab Dis 2007;30:51–9.
4. Winsor EJ, Welch JP. Genetic and demographic aspects of Nova Scotia Niemann–Pick disease (type D). Am J Hum Genet 1978;30:530–8.
5. Garver WS, Francis GA, Jelinek D et al. The National Niemann–Pick C1 database: report of clinical features and health problems. Amer J Med Genet Part A 2007;143A:1204–11.
© 2007 Blackwell Publishing Limited. Reproduced by permission.