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 Table of Contents  
REVIEW ARTICLE
Year : 2017  |  Volume : 1  |  Issue : 2  |  Page : 105-112

Geographical distribution of cystic fibrosis; The past 70 years of data analyzis


1 Mycobacteriology Research Center (MRC), National Research Institute of Tuberculosis and Lung Disease (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran
2 Department of Biotechnology, School of Advanced Technologies in Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
3 Paediatric Respiratory Diseases Research Center, National Research Institute of Tuberculosis and Lung Diseases (NRITLD), Shahid Beheshti University of Medical Sciences, Tehran, Iran

Date of Web Publication23-Nov-2017

Correspondence Address:
Poopak Farnia
Department of Biotechnology, School of Advanced Technologies in Medicine, Shahid Beheshti University of Medical Sciences, Tehran
Iran
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/bbrj.bbrj_81_17

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  Abstract 


Cystic fibrosis (CF) has been generally well defined throughout the world although its prevalence is very difficult to ascertain for a number of reasons, including the fact that the medical/scientific literature and patient registries vary in quality in different countries. In the present review literature (1938–2017), we found out the higher frequency of registered CF patients in the European Union. This could be due to strong clinical awareness and greater health facilities. In contrast, we found a very irregular report from Asian and African countries. In these countries, the national CF registration system is mostly lacking or it is individualized-based research. In this situation, the estimation of various risk factors such as ethnicity and/or races is remained to be resolved. Overall, this review outlines the urgent need for revitalization of national and global CF registration, worldwide.

Keywords: Cystic fibrosis, ethnicity, geographical distribution


How to cite this article:
Mirtajani SB, Farnia P, Hassanzad M, Ghanavi J, Farnia P, Velayati AA. Geographical distribution of cystic fibrosis; The past 70 years of data analyzis. Biomed Biotechnol Res J 2017;1:105-12

How to cite this URL:
Mirtajani SB, Farnia P, Hassanzad M, Ghanavi J, Farnia P, Velayati AA. Geographical distribution of cystic fibrosis; The past 70 years of data analyzis. Biomed Biotechnol Res J [serial online] 2017 [cited 2018 Sep 22];1:105-12. Available from: http://www.bmbtrj.org/text.asp?2017/1/2/105/219112




  Introduction Top


Cystic fibrosis (CF) is an autosomal genetic disease (i.e., not sex linked) that causes an accumulation of mucus in exocrine- and exocrine-associated organs.[1],[2],[3] The main symptoms include a persistent cough that produces mucous, recurrent lung infection, intestinal obstruction, malabsorption, nasal polyps, rectal prolapse, pancreatitis, increase of blood sugar level, and growth hormones disorders [Figure 1].[1],[4] Therefore, the main effected organs in CF diseases are respiratory, digestive, and reproductive tracts. Lungs in CF diseases lose their ability to maintain a sterile surface. That is, these organs will be damaged by bacterial infections gradually.[5] The amount of intestinal fluid is lower than normal; hence, after a dehydration of the stool, patient will suffer from bowel obstruction.[6] The pancreatic duct also secretes less fluid than normal, causing ductal blockage and eventually pancreatic degeneration. As a result, loss of pancreatic enzymes causes steatorrhea that may offset the tendency for intestinal block.[7] Generally, CF is mainly appeared in infants and childhood. The bases of CF are the mutation that occurs in CFtransmembrane conductance regulator (CFTR) gene.[1],[8] The CFTR gene is located on chromosome 7q31.2 and consists of 27 exons.[9] This gene produces CFTR protein, a member of the ATP Binding Cassette family. CFTR protein presents on epithelial cells of many organs including the lung, liver, pancreas, digestive tract, and reproductive tract. Normally, CFTR protein controls the flow of chloride and thiocyanate ions across the epithelial cells.[10] Indeed, ions freely flow in and out of the cells while CFTR works properly. However, if CFTR does not work correctly, ions cannot cross the membrane. As a result, thickened mucous is formed in the lung, pancreas, and other organs.[11] This sticky mucus obstructs the airways and glands. In addition, it causes the bacterial trapping. So far, several mutations in CFTR genes have been reported, of which mutations in ΔF508, N1303K, G542X, 1717-1G>A, R553X, W1282X, G551D, 621 + 1G > T, ΔI507, and R560 had gained more clinical attention.[12],[13],[14] The most frequent mutation is identified as ΔF508.[15] This mutation acts by eliminating phenylalanine at position F508. Thus, the protein would not fold normally and is more quickly would be degraded.[16] The extent and complication of CF are due to polymorphisms in CFTR gene. In fact, it is highly variable in different populations.[8] In the present investigation, we tried to review the incidence of reported CF cases in different continents of the world.
Figure 1: Signs and common disorders of the disease cystic fibrosis. These symptoms are different in different patients, and patients with one or more different emblem refer

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Background

There is no exact document showing when the first clinical case of CF was identified. References have been found in medical texts as early as 1595 which linked salty skin and damage of the pancreas with death in childhood by infants who were “hexed” or “bewitched.”[17] In this regard, Pieter Pauw (1564-1617) performed the first autopsy of an 11-year old female child in the anatomical theater in Leiden. He showed that the death was due to oddly swollen pancreas.[17] Thereafter, in 1606, Alonso y de los Ruyzes de Fonteca, Professor of Medicine at Henares in Spain, described the salty taste of infants with CF.[18] In the mid-sixteenth century, steatorrhea was recognized as an indicator of CF.[19],[20] Moreover, Samuel Gee in 1888 reported digestive tract problems in CF patients, i.e., arrest of growth, a distended abdomen, and attacks of diarrhea with large, pale, foul-smelling stools.[21] These symptoms were as a result of the injury and clear change of pancreatic function. Furthermore, Landsteiner (1905), who also has defined blood groups, published the report on association of meconium ileus with defective CF pancreas.[22] Later on, from 1930 to 1940, many findings were obtained about CF. Indeed, the terminology of CF began to develop during the 1930s. During these years, the descriptions focused on pancreatic disorders, steatorrhea, and bronchopulmonary complications. Of this, Fanconi et al. in 1936 referred the diseases as cystic fibrosis with bronchiectasis and have separated it from celiac disease. Besides, in other work by Anderson in 1938, the term “CF of the pancreas” was used.[23] Further, in 1945, Farber had introduced the term “mucoviscidosis” (state of thickened mucus that causes the diseases) instead of what Anderson has proposed. This term still is in use in non-speaking English countries.[24] As a matter of fact, first researchers who provided compelling evidence about source of CF were Andersen and Hodges in 1946.[25] They reported CF as a genetic disorder as well as stems in an autosomal recessive mutation. In the next 6 years, Sant' Agnese from Columbia discovered the dissolution of salt (sodium chloride) as a disease index in patients with CF. Quickly, the sweat test became a most reliable diagnostic test to identify patients with CF.[26] However, to clarify the clearest criteria, both pathological demonstrations such as (abnormal thick or sticky mucus or proteinaceous in the lumens of pancreas, lung, and intestine) and abnormal salty secretions of sweet glands are required. Further research revealed the differences in age and gender in CF. Generally, the incidence of this disease in children is higher than in adults.[27] According to the published studies in European countries, there are approximately four CF children for every three CF adults.[28] A study by McCormick et al. (2010) showed that 53% of patients were under 18 years of age and only 5% of CF patients could survive over 40 of age.[29] Although, in Asian countries, CF children are between 1 and 5 years of ages, majority of them expired within first 5 years of their live.[30],[31] Besides the age, the gender was reported in correlation with CF development and survival. For instance, in an investigation conducted in Europe, the ratio of men with CF was 1.1 folds more than women. This means that about 53% of the reported patients in Europe were male.[32] These results are widely acknowledged by other researchers. On the other hand, according to a study published in 1985 by Sturgess et al., the CF development in Canadian men was 53.57% of the total population.[33] In this regard, Dodge et al. reported the survival rate of 55% for CF male patients and 49% for CF female patients. Moreover, the patient's data reported as 91% in 1988 and 88% in 1992. Furthermore, in 1997, it was 96%. The estimated CF population in mid-year of 2003 was 8284.[34] As shown in the previous studies, most of reported CF patients are children, and the frequency of infection in male is 6%–8% higher than female subjects [Figure 2] and [Figure 3].[30],[31],[32],[33],[34] To summarize and analyze various evidence-based research on CF, different public health organization tried to launch a national level of CF registry. Among these organizations, CF Foundation in the United Stated of America (USA) (1955); Canadian CF Foundation (1959), United kingdom of CF Trust (1964), and Vaincre la Mucoviscidose (1964) can be named. Subsequent to these countries, many more CF foundation has established worldwide.[21] Finally, the International Organization for CF was formed in 1964 in Paris.[21] Through this organization, various research activities including pathological, molecular, treatment protocols and epidemiological investigations in relation with CF were established.
Figure 2: Distribution of patients with age-related cystic fibrosis in the UK over 56 years (1947–2003)

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Figure 3: The proportion of patients with cystic fibrosis based on the gender of patients

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  Methods Top


Literature search strategy

This manuscript is a review of previous published studies in various continents during 1938–2017. All articles used in this study were collected from Scopus, PubMed, Google Scholar, and ScienceDirect using the keywords of “cystic fibrosis,” “distribution of CF,” and “Epidemiology of CF.”

Inclusion and exclusion criteria

The subjects of used articles were about distribution, epidemiology, genetics, and pathology of patients with CF. In total, 341 articles used for evaluation; 92 articles (review, original and case report articles and books) were selected.

Epidemiology of cystic fibrosis

Today, clinical epidemiology means an investigation that shows the incidence of disease in human populations.[35] Practically, epidemiological studies reveal measurable parameters for understanding the root and pattern of transmission within specific communities.[35] This ability will help policymakers to design general policies about the disease.[36] During recent years, many investigators had focused on frequency and/or prevalence of CF.[32],[37] Previous studies showed variable prevalence of CF among different races [Figure 4]. In addition, Hill et al. (1998) suggested the frequent incidence of CF among Whites. Later on, this observation was confirmed by Westwood et al. in 2007.[38] In another multicenter study that conducted in 27 European countries, the CF incidence was rated as 0.073% of total population.[39] A variety of risk factors such as racial purity, the immigration, racial integration, mutation, and sometimes environmental factors can be considered as disease development.[1],[8],[40] However, distribution of risk factors can be variable in different population.[41],[42],[43] Thereby, in the present study, the various risk factors in different continent were highlighted separately.
Figure 4: The above picture shows the difference in the distribution of outbreaks in different continents. Accordingly, the highest rates in Europe and lowest is in East Asia

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Asia

The statistical analysis of the various continents regarding prevalence of CF showed that Asia has the lowest rate of patients with the disease [Figure 5]. According to data from the World Health Organization (WHO), there is no detailed information on the prevalence of CF in Asia.[44] Although this can be due to lack of registration, we know that many Asian countries do not have the national CF registration.[45] Furthermore, available data have gathered from case series studies or individualized hospital reports. Based on what is available, the number of reported CF patients in West Asia is one in every 4000–10,000 people, while the number in East Asia is much lower, i.e., one case in every 100,000–350,000.[31],[46] For instance, in India as a country in West Asia, the prevalence of CF is one case per 43,321–100,323 people. In addition, the statistics in Japan is (in the East) one case per 350,000 people.[47] Among other Asian countries, the Middle-Eastern ones have very limited information [Figure 6].[47],[48],[49],[50],[51] This is again can be due to lack of National CF Registry and/or improper reporting system. In addition, lack of medical awareness as well as premature deaths as results of undiagnosed treatment is worsening the situation. Based on average statistical analysis in the Middle East, one in every 2560 to 15,876 cases was developed CF [Figure 4].[46] The incidence is variable among different regions, e.g., one patients reported in Bahrain within the last 15 years. In contrast, 11 CF infants reported in 1 year in Lebanon.[48],[49] The reported rate for Iran was 1 in 100,000.[50] In addition, research studies revealed a mutation at F508del in CFTR gene in the majority of CF patients. In this regard, the frequency of mutation at F508del in CFTR gene was 37.5%; 24%, and 18%–23% in Lebanon, Turkey, and Iran, respectively.[12],[52],[53],[54],[55],[56],[57] Investigators suggested that inter-familial marriage in these regions is a crucial risk factor for CF development.[46]
Figure 5: The incidence of cystic fibrosis on the map according to the World Health Organization

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Figure 6: The distribution of patients with cystic fibrosis in a number of countries in the Middle East. According to the above-mentioned data, lack of uniform distribution is visible

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Africa

The first report of CF refers to 1959[57] in a South African newborn. This child died shortly after birth due to meconium ileus.[58] In addition, during the next 3 years, different cases were reported in various regions of the African continent.[59],[60] However, due to geographical and geopolitical situation, the in-depth investigation remains obscure.[58],[59] In addition, few studies demonstrated importance of mutation in the gene CFTR (3120 + 1G → A) among African nations.[58] The Official WHO statistics show a 70%–79% mutation outbreak in the CFTR genes, in Tunisia and Algeria.[61] According to a study published in (1999), the prevalence of CF among African population in the south region was higher than people living in the East and West of Africa. Indeed during 1998–2000, no cases of CF were reported from the western region of Africa.[58] Possibly, through this period, most of health care authorities were involved in deceasing malnutrition, poverty, and/or controlling the deadly spread of tuberculosis and HIV infection.[62],[63]

North America

Frequency of CF in North America is 1 out of every 2500 people.[64] However, there are differences in its distribution across the American continent. The prevalence of CF in the US Whites is 1 in every 2900 babies.[64] In Canada, the data are 1 in every 2500 babies [Figure 7].[64],[65],[66],[67] This can be due to differences of ethnicity or races in North America. The White races are higher than other races, i. e., Native Americans, Hispanics, and Blacks,[64],[66] and since White races have higher racial purity, they might be more prone to develop CF, which needs further investigation.
Figure 7: Distribution of cystic fibrosis patients in North America. According to Figure 5, cystic fibrosis prevalence rate in Whites, more than any other American races

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South America

South America as a continent with enormous racial disparity has a high distribution of CF patients. Outbreaks on the continent were depending on regions and countries of residence between 1 case in 3500 and 8500 people.[68],[69] [Table 1] shows the distribution of CF patients in four countries of Latin America.[70] Accordingly, the distribution of CF in the northern region (Mexico), South (Argentina), then to the East (Brazil), and West (Chile) shows a higher number. In the meantime, it shows the highest level of contamination in Southern Argentina.[70] Adverse economic conditions such as high mortality due to disease,[70] lack of proper diagnosis, and management of respiratory infections are factors which affecting the figures on the distribution of this disease.[71]
Table 1: People with cystic fibrosis in Latin America, between 1968 and 1989

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Europe

In comparison with other continents, Europe is reported to have the highest level of CF. The high prevalence of CF in Europe has caused countries in the continent to carry out severe screening programs for this disease.[72],[73] Existing programs such as nail-patella syndrome for genetic disease screening helped to make this decision.[74] With the establishment of the European CF Society (ECFS) in 2004, the process has been speeding up.[75] The high level can be as a result of proper registry and strong clinical awareness. In Europe, there is a very well organized registration system which maintained by the ECFS.[67] Acquired data from both national CF registries and individual CF centers would enter to the systems on regular bases throughout Europe.[76],[77] Therefore, the picture of CF is very clear cut in Europe [Figure 8].[21]
Figure 8: The number of dead people with cystic fibrosis in Europe (divided year and country)

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As shown in [Table 2], the distribution of CF is more dramatic in northern, northwestern, and central Europe.[39] Indeed, Farrell et al. in 2007 reported the highest birth rate of CF (1 in 1353 people) in Ireland.[78] However, Germany with 82/425 patients had the highest number of patients.[79],[80] Among countries located in the northern region of Europe, the Finland showed the lowest rate of CF disease (1 in 25000 people).[78],[80] On the other hand, other parts of Europe are all homogeneous in this regard approximately.[46],[84] This is probably stems in proximity between the races, and the racial mixing.[85] In fact, studies showed that F508del mutation in gene CFTR is more frequent (70%) among European patients among European patients.[46]
Table 2: Distribution to cystic fibrosis patients in the countries of Europe

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Oceania

As racial differences in Australia, the incidence and distribution of CF patients are variable [Figure 9].[86],[87],[88],[89] The highest prevalence in Australia is related to the Britain immigrants, with 1 case in every 2021 birth. Although for other races the rate is decreased by 2.5 folds.[85]
Figure 9: Distribution of cystic fibrosis patients in Australia and New Zealand

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  Conclusion Top


As shown, a considerable number of countries, especially those located in Africa, parts of Asia, and parts of the South America, have no or limited registration system. It is understandable that health authorities in these countries have no choice but ignoring CF that is due to other important and priorities in public issues, for instance, civil war, poverty, malnutrition, and outbreaks of infectious diseases such as tuberculosis. The policy in these regions needs to be reviewed. According to the collected information, it is realistic to acclaim that more than 50% of countries in different continents have no information. This situation has already been discussed in global policy. As a consequence, the WHO has already listed the CF as important disease and asked all countries to update their data and reports on CF cases. This will ultimately make the countries to plan for National Registry of CF. Hopefully, within the next few years, the global distribution of diseases and other strategically plans become possible.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9]
 
 
    Tables

  [Table 1], [Table 2]


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