Monitoring congenital rubella embryopathy

BACKGROUND

Currently, all developed countries include rubella vaccination in their immunization programs, targeting the complete elimination of congenital rubella syndrome (CRS). In the underdeveloped world, where this severely disabling condition still exists, only a few countries have implemented vaccination policies, and almost no data on their effectiveness or on prevalence rates are available. The aims of the present work were to search for the best phenotype to be used as a sentinel for CRS in a large series of malformed newborns and to propose a CRS surveillance system, based only on clinical data.

METHODS

A total of 43 infants diagnosed as having CRS were obtained from 19,184 multimalformed infants, ascertained by the Latin-American Collaborative Study of Congenital Malformations, World Health Organization (WHO) Collaborating Centre for the Prevention of Birth Defects (ECLAMC), over 3,883,165 consecutive births, between 1982 and 2003. They were distributed by country and the most frequent birth defects were identified. From the 19,184 multimalformed infants, all cases presenting the birth defects identified were selected. The sensitivity, specificity, and likelihood ratio (LR) in detecting CRS were determined for these birth defects, alone and in combination. The sample size of multimalformed infants required to detect different levels of increase in the rate of CRS was determined for three sentinel phenotypes.

RESULTS

The rate of CRS was highest in Brazil. Based on the best possible combination of sensitivity, specificity, and LR, the dyad comprising eye anomalies and congenital heart defects was shown to be the most appropriate sentinel, with the lowest sample size required, to detect CRS in neonates.

CONCLUSIONS

A surveillance system for CRS, based on clinical data in newborns, is being proposed, in an attempt to monitor ongoing vaccination policies, aimed at eliminating CRS in developing countries.

Interferon regulatory factor 6 (IRF6) gene variants and the risk of isolated cleft lip or palate

BACKGROUND

Cleft lip or palate (or the two in combination) is a common birth defect that results from a mixture of genetic and environmental factors. We searched for a specific genetic factor contributing to this complex trait by examining large numbers of affected patients and families and evaluating a specific candidate gene.

METHODS

We identified the gene that encodes interferon regulatory factor 6 (IRF6) as a candidate gene on the basis of its involvement in an autosomal dominant form of cleft lip and palate, Van der Woude's syndrome. A single-nucleotide polymorphism in this gene results in either a valine or an isoleucine at amino acid position 274 (V274I). We carried out transmission-disequilibrium testing for V274I in 8003 individual subjects in 1968 families derived from 10 populations with ancestry in Asia, Europe, and South America, haplotype and linkage analyses, and case-control analyses, and determined the risk of cleft lip or palate that is associated with genetic variation in IRF6.

RESULTS

Strong evidence of overtransmission of the valine (V) allele was found in the entire population data set (P<10(-9)); moreover, the results for some individual populations from South America and Asia were highly significant. Variation at IRF6 was responsible for 12 percent of the genetic contribution to cleft lip or palate and tripled the risk of recurrence in families that had already had one affected child.

CONCLUSIONS

DNA-sequence variants associated with IRF6 are major contributors to cleft lip, with or without cleft palate. The contribution of variants in single genes to cleft lip or palate is an important consideration in genetic counseling.

Is there a familial link between Down's syndrome and neural tube defects? Population and familial survey

OBJECTIVE

To verify whether Down's syndrome and neural tube defects arise more often in the same family than expected by chance.

DESIGN

Population and familial survey.

SETTING

Network of maternity hospitals in the Latin American collaborative study of congenital malformations (ECLAMC) in Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Paraguay, Peru, Uruguay, and Venezuela between 1982 and 2000.

PROBANDS

2421 cases of neural tube defects, 952 of hydrocephalus, and 3095 of Down's syndrome registered from a total of 1 583 838 live births and stillbirths.

MAIN OUTCOME MEASURES

Observed number of cases of Down's syndrome among siblings of probands with a neural tube defect or hydrocephalus and number expected on the basis of maternal age; observed number of cases of neural tube defects or hydrocephalus among siblings of probands with Down's syndrome and number expected according to the prevalence in the same population.

RESULTS

Five cases of Down's syndrome occurred among 5404 pregnancies previous to a case of neural tube defect or hydrocephalus, compared with 5.13 expected after adjustment by maternal age. Twelve cases of neural tube defect or hydrocephalus occurred among 8066 pregnancies previous to a case of Down's syndrome, compared with 17.18 expected on the basis of the birth prevalence for neural tube defects plus hydrocephalus in the same population.

CONCLUSION

No association occurred between families at risk of neural tube defects and those at risk of Down's syndrome.

Sex ratio and associated risk factors for 50 congenital anomaly types: Clues for causal heterogeneity

BACKGROUND

Sex ratio (SR) deviations have been reported for many congenital anomalies, but so far no satisfactory explanation for these deviations has been found. The aim of this study was to detect sex-related differences in the association between risk factors and congenital anomalies, and to relate these differences with possibly underlying causes of birth defects.

METHODS

Between 1982 and 1999, 1,444,646 newborn infants were examined by the Estudio Colaborativo Latino Americano de Malformaciones Congénitas (ECLAMC) network of South American maternity hospitals. Male relative risks were established for 39,425 infants with 50 selected single anomalies. Associations between male sex and risk factors were identified in nonmalformed infants. In malformed infants, sex-related risk differences were established, and the SR of these infants, with and without associated risk factors, were compared.

RESULTS

Infants with neural tube defects (NTDs) and intrauterine growth restriction had a lower SR than those with normal growth, while spina bifida without hydrocephaly (SB[sHy]) was the only NTD subtype without a significant female predominance. Multigravidity lowered the SR of SB(sHy) and HPP (HPP) cases. Increased paternal age inverted the SR of cleft lip (CL) with or without cleft palate (CL[P]) cases from male to female.

CONCLUSIONS

The results indicate etiological differences between high and low SB, a stronger relationship between multigravidity and female sex of the offspring than between multigravidity and a specific congenital anomaly, and a possible involvement of dominant mutations for CL(P), as suggested by the association with increased paternal age.

Relation between oculo-auriculo-vertebral (OAV) dysplasia and three other non-random associations of malformations (VATER, CHARGE, and OEIS)

Using a statistical methodology, we aimed to identify a group of probable cases of oculo-auriculo-vertebral (OAV) dysplasia and to investigate possible relationships between different patterns of congenital malformations. Among 5,260 infants with multiple malformations collected from 4 large registers of congenital malformations, we identified 312 probable OAV cases. With the same technique, we have earlier defined epidemiological delineations of three other well-known non-random associations of congenital malformations (CHARGE, VATER, and OEIS). We found convincing relationships between OAV and VATER or CHARGE but none between OAV and OEIS or between the three malformation complexes CHARGE, VATER, and OEIS. An association between two conditions indicates similarities in pathogenesis or in etiology. We suggest that the connection between OAV and CHARGE could be related to a common pathogenetic mechanism: disturbed neural crest development.

Preliminary data on changes in neural tube defect prevalence rates after folic acid fortification in South America

Several South American countries are fortifying wheat flour with folic acid. However, only Chile started in 2000 to add 2.2 mg/kg, providing 360 microg daily per capita, an acceptable dosage for preventing the occurrence of some neural tube defect (NTD) cases. ECLAMC (Spanish acronym for the Latin American Collaborative Study of Congenital Malformations) routinely monitoring birth defects in South America since 1976, surveyed the impact of this fortification. Data from 361,374 births occurred in 43 South American hospitals, distributed in five different countries, active throughout the 1999-2001 triennium, were selected from the ECLAMC network. Birth prevalence rates for three different congenital anomalies with similar expected prevalence rates, were surveyed by the Cumulative Sum Method (CUSUM) method. They were NTD, oral clefts (OC), and Down syndrome (DS). Expected values were derived from observations made in 1999, and CUSUM was applied to the consecutive series of 24 months covering years 2000 and 2001. Only one of three congenital anomaly types, NTDs, in only one of five sampled out countries, Chile, showed a significant decrease, of 31%, during the 2000-2001 biennium, corresponding to the birth of the periconceptionally fortified infants. The level of significance (P < 0.001) was reached in the 20th month after fortification started, corresponding to August 2001. This is the first observation of a significant decrease in the occurrence of NTD after folic acid food fortification in a population little influenced by confounders common in the developed world as pre-existing secular decreasing trends, and partially unregistered induced abortions.

Complete sequencing shows a role for MSX1 in non-syndromic cleft lip and palate

MSX1 has been proposed as a gene in which mutations may contribute to non-syndromic forms of cleft lip and/or cleft palate. Support for this comes from human linkage and linkage disequilibrium studies, chromosomal deletions resulting in haploinsufficiency, a large family with a stop codon mutation that includes clefting as a phenotype, and the Msx1 phenotype in a knockout mouse. This report describes a population based scan for mutations encompassing the sense and antisense transcribed sequence of MSX1 (two exons, one intron). We compare the completed genomic sequence of MSX1 to the mouse Msx1 sequence to identify non-coding homology regions, and sequence highly conserved elements. The samples studied were drawn from a panethnic collection including people of European, Asian, and native South American ancestry. The gene was sequenced in 917 people and potentially aetiological mutations were identified in 16. These included missense mutations in conserved amino acids and point mutations in conserved regions not identified in any of 500 controls sequenced. Five different missense mutations in seven unrelated subjects with clefting are described. Evolutionary sequence comparisons of all known Msx1 orthologues placed the amino acid substitutions in context. Four rare mutations were found in non-coding regions that are highly conserved and disrupt probable regulatory regions. In addition, a panel of 18 population specific polymorphic variants were identified that will be useful in future haplotype analyses of MSX1. MSX1 mutations are found in 2% of cases of clefting and should be considered for genetic counselling implications, particularly in those families in which autosomal dominant inheritance patterns or dental anomalies appear to be cosegregating with the clefting phenotype.

Inheritance of cleft palate in South America: evidence for a major locus recessive

OBJECTIVES

Determine the model of inheritance of non-syndromic cleft palate in humans.

DESIGN

Complex segregation analysis performed in families of consecutive newborns affected with non-syndromic cleft palate.

SETTING AND SAMPLE POPULATION

The Latin American Collaborative Study of Congenital Malformations (ECLAMC). Four hundred and seven consecutive newborns affected with non-syndromic cleft palate registered during the period 1967-97.

OUTCOME MEASURE

Likelihood ratio test and Akaike information criterion (AIC) values.

RESULTS

The single major locus recessive model provided a significantly better explanation of the data. It was the most parsimonious and had the smallest AIC value of the six models tested with approximately the same likelihood as the general model (chi2 = 2.44, p = 0.5).

CONCLUSIONS

To have defined a genetic model for non-syndromic cleft palate and provided evidence for a single major locus inheritance suggests that genetic linkage studies could be implemented.

Clinical and epidemiological studies of amniotic deformity, adhesion, and mutilation (ADAM) sequence in a South American (ECLAMC) population

Amniotic deformity, adhesion, and mutilation (ADAM) sequence is a heterogeneous condition, with a broad spectrum of anomalies, where intrinsic causes, as defect of germ plasm, vascular disruption, and disturbance of threshold boundaries of morphogens during early gastrulation, alternate with extrinsic causes as amniotic band rupture to explain the condition. This study aimed to identify which phenotypes could be considered as ADAM sequence, determine the prevalence rate, and disclose risk factors for this sequence. We identified 270 cases defined as having some skin evidence of constriction band, plus those having limb defects suggestive of ADAM sequence, among 3,020,896 live and stillborns in the years 1982 to 1998 in ECLAMC (Latin American Collaborative Study of Congenital Malformations). Half of the cases presented mutilation (reduction), and deformity (ring constriction) affecting distal parts of fingers or toes bilaterally, without associated defects. Acrania, cephalocele, typical or atypical facial clefts, eyelid coloboma, and celosomia were also observed being significantly associated with the skin lesion. One affected infant in every 11,200 births, was found with stable trends during the last 17 years. There was an excess of cases in populations living at high altitude, stillborns, and neonatal infant dead. Among ADAM cases there was an excess of mothers with a prenatal history of febrile acute illness, medication drug use, or vaginal bleeding during the first trimester of pregnancy. Higher than expected frequencies of first-born child, premature birth, low birth weight for gestational length, and non-cephalic fetal presentation were also found. The observed geographic difference in birth prevalence could be a useful indication to study specific genetic and environmental candidate factors to ADAM susceptibility.

MSX1 and TGFB3 contribute to clefting in South America

MSX1 and TGFB3 have been proposed as genes in which mutations may contribute to non-syndromic forms of oral clefts; however, an interaction between these genes has not been described. The present study attempts to detect transmission distortion of MSX1 and TGFB3 in 217 South American children from their respective mothers. With transmission disequilibrium test analysis, cleft lip with/without cleft palate, cleft lip with palate plus cleft palate only, and all datasets combined showed evidence of association with MSX1 (p = 0.004, p = 0.037, and p = 0.001, respectively). With likelihood ratio test analysis, "cleft lip only" showed association with MSX1 (p = 0.04) and "cleft palate only" with TGFB3 (p = 0.02). A joint analysis of MSX1 and TGFB3 suggested that there may be an interaction between these two loci to increase cleft susceptibility. These results suggest that MSX1 and TGFB3 mutations make a contribution to clefts in South American populations.

Genetic origins in a South American clefting population

It has been proposed that susceptibility to clefting in South America is related to Amerindian ancestry, where clefting is present at a higher frequency than in the other admixed populations (Caucasian and African) that make up the diverse racial mix of current South Americans. To clarify the genetic origins and establish a method for genetic mapping, mitochondrial DNA variation and Y-chromosome markers were studied in a South American population affected with clefting. Two-hundred and seventeen subjects and matched controls were selected through the Latin-American Collaborative Study of Congenital Malformations (ECLAMC). The case group showed a higher frequency of Native American haplogroups and a lower frequency of African haplogroups (p < 0.00001). In addition, the case group showed a much higher frequency of the specific native American haplogroup D than the control group (p < 0.00001). For the Y-chromosome markers, the case group showed a lower frequency of the African-specific marker, YAP (p = 0.002), and a higher frequency of the Native American-specific marker, DYS199 (p < 0.00001). Even though differences were found in the frequencies of the markers studied, the contribution of each founder population was similar for both groups. Results suggest a strong Native American maternal contribution and a strong Caucasian (Spanish and Portuguese) paternal contribution to the population studied. The implications of this finding include the possibility of using admixture mapping approaches to this population.

Endocrine disruptors and congenital anomalies

The specialized literature was reviewed concerning the suspected increasing secular trends in the frequency of female births, male genital congenital anomalies, abnormal sperm counts, and testicular cancer. Although no risk factors could be identified yet, the observed sex ratio decline during the last decades has been considered to be an effect of certain pollutants on normal hormone activity, and human reproductive development. Reported increasing trends in the frequencies of hypospadias and cryptorchidism are very difficult to be interpreted due to the large variability in the registered frequency of these malformations due to operational as well as biological reasons.

Mutational analysis of the Sonic Hedgehog gene in 220 newborns with oral clefts in a South American (ECLAMC) population

Oral clefts generally have a multifactorial etiology. A number of genes contribute to the formation of the face and palate. Cleft lip and/or palate can occur in pedigrees with autosomal dominant holoprosencephaly due to mutations in Sonic Hedgehog (SHH). In addition, animal models have shown that SHH is involved in face development. We thus examined the human SHH gene in 220 newborn infants with nonsyndromic oral clefts registered by the Estudio Colaborativo Latinoamericano de Malformaciones Congenitas: ECLAMC (Latin American Collaborative Study of Congenital Malformations). We found 15 variant bands in 13 patients with oral clefts, representing five different base changes, all of which were found by sequencing to represent silent polymorphisms. Four occurred in introns. The alteration occurring in an exon, Ser190Ser, may create a consensus sequence for the 3'splice site 6 bp downstream of the original consensus sequence. Thus, we did not identify any clearly disease-causing mutation in SHH in these patients, and conclude that SHH mutations are not a frequent cause of isolated oral clefts in humans.

Risks of congenital anomalies in large for gestational age infants

OBJECTIVES

To evaluate the association between large for gestational age (LGA) and demographic and medical risk factors as well as specific types of congenital anomalies.

STUDY DESIGN

A retrospective, case-control study on 2,149,617 consecutive births was conducted. LGA was defined as 1.64 SD above the mean weight for gestational age, adjusted by sex and altitude. Risk factor frequency distributions were compared between LGA and normal birth weight neonates. Associations between LGA and 41 infants with isolated congenital anomalies were evaluated.

RESULTS

Of 31,897 neonates with congenital anomalies, 1800 were LGA. Five anomalies were associated with LGA: talipes calcaneovalgus, hydrocephaly, combined angiomatoses, hip subluxation, and non-brown-pigmented nevi. Multiparity, vaginal bleeding, diabetes, and delivery by cesarean section were more frequent in LGA than in appropriate for gestational age infants' mothers. Several maternal but no paternal factors were statistically associated with an increased risk for LGA infants.

CONCLUSIONS

The clinical observation that nevi are more commonly observed in LGA patients was supported. The higher frequencies of hip subluxation and talipes calcaneovalgus among LGA neonates reinforces their pathogenesis as deformations, whereas those of combined angiomatoses and hydrocephaly could reflect increased fluid or body mass.

Epidemiological methods to assess the correlation between industrial contaminants and rates of congenital anomalies

The present knowledge of epidemiological methods, applied to assess the correlation between industrial contaminants and rates of congenital anomalies is reviewed. The concept of congenital anomalies may be extended to include other adverse reproductive outcomes, such as malformations, infant mortality, stillbirths, spontaneous abortions, intrauterine growth retardation, ectopic pregnancies, multiple births, altered secondary sex ratio, and parental sub-fertility. The review of occupational exposures associated with congenital anomalies indicated: (1) inconsistency of the reported associations; (2) more positive than negative associations; (3) solvents are the best studied, and the most frequently reported teratogenic chemicals; (4) common congenital anomalies are the most frequently studied diagnostic categories, while other defects are grouped into larger categories, with little biological meaning. The review of environmental exposures indicated that: (1) single-site studies outnumber multi-site ones; (2) results are heterogeneous; (3) congenital anomalies are, in general, unspecific, and grouped into large categories, such as those defined by anatomic systems. Recent developments in molecular biology anticipate the possibility to measure exposures directly, instead of by different "proxies", as well as to analyze the genetic predisposition for the teratogenic response to given environmental agents. The strategy of building up large banks of biological materials has already started in several birth defects registries. The following procedural guidelines to assess the teratogenicity of a pollutant are recommended: (1) strength of the association; (2) consistency of findings in different studies; (3) specificity of the association; (4) time-exposure relationship; (5) existence of a dose-response gradient between exposure and disease occurrence; (6) biological plausibility; (7) coherence of the evidence with natural history of the disease; (8) experimental (or quasi-experimental) evidence and (9) reasoning by analogy.

Search for ethnic, geographic, and other factors in the epidemiology of Down syndrome in South America: analysis of data from the ECLAMC project, 1967-1997

We have analyzed data on 3,157 cases of Down syndrome (DS) from nine South American countries in consecutive series of hospital live births over a 30-year period, with particular emphasis on possible ethnic or geographic variations in maternal age-adjusted incidence. The data constitute the largest series of DS cases assembled to date from an area lacking advanced health care systems. Absolute incidence rates were estimated from total hospital live births; relative rates were estimated from matched case-control data using conditional logistic regression. Maternal age-adjusted rates were closely similar to those reported elsewhere, and showed little or no dependency on other factors investigated, including paternal age, birth order, ancestral origin, country of birth, maternal educational level, maternal ABO and Rhesus blood groups, interval to and outcome of mother's previous pregnancy, and parental consanguinity. The absence of an effect of high birth order was particularly notable because of the relatively large number of grand multipara resulting from high fertility in this population. The study adds to a body of evidence suggesting that maternal age-adjusted DS rates vary little across human populations, and are therefore unlikely to be greatly influenced by genetic or environmental factors that differ between them. An unusual finding was of a markedly lower sex ratio (98 males per 100 females) than has been reported in other DS samples.

Parental consanguinity in specific types of congenital anomalies

Parental consanguinity, as a recognized risk factor for congenital anomalies, has mainly been studied with a focus on the types of parental relationships and their effects on genetic syndromes or birth defects in general. The present work analyzed the association between parental consanguinity and congenital anomalies, split, when possible, into clinical subtypes, in an attempt to obtain some insight into their recognized etiological heterogeneity. The material consisted of 34,102 newborn infants, affected by one of 47 selected congenital anomaly types, ascertained by the Latin-American Collaborative Study of Congenital Malformations (ECLAMC) during the period from 1967 to 1997. The consanguinity rate for each congenital anomaly type was compared with that of the population under study (0.96%), and the potentially confounding effect of six selected variables was controlled through a conditional logistic regression analysis for those congenital anomalies significantly associated with consanguinity. Pre-occurrence rates for the same congenital anomaly in sibships of consanguineous and non-consanguineous cases were compared. A significant association with parental consanguinity was observed for three congenital anomaly types: hydrocephalus, postaxial hand polydactyly, and bilateral cleft lip +/- cleft palate, while three additional anomalies, namely, cephalocele, microcephaly, and hand + foot postaxial polydactyly, showed a positive association, but statistical significance disappeared after adjustment for confounders, probably owing to sample size reduction. The association between consanguinity and Down syndrome was mainly due to the confounding effect of maternal age, while for hydrops fetalis and 2-3 toe syndactyly, the observed positive association could not be tested for confounders due to sample size reduction.

Identification of novel mutations in SHH and ZIC2 in a South American (ECLAMC) population with holoprosencephaly

Holoprosencephaly (HPE) is genetically heterogeneous with four genes, SIX3, SHH, TGIF, and ZIC2 that have been identified to date and that are altered in 12% of patients. To analyze this prevalence in a South American population-based sample (57 HPE cases in 244,511 live and still births or 1 in 4300), we performed a mutational study of these genes in 30 unrelated children (26 newborns and 4 non-newborns) with HPE being ascertained by ECLAMC (Latin American Collaborative Study of Congenital Malformations). We identified three novel mutations: two were missense mutations of the SHH gene (Cys183-->Phe; His140-->Pro); the third mutation was a 2-bp deletion in the zinc-finger region of the ZIC2 gene. These molecular results explained 8% (2/26 newborn samples) of the HPE cases in this South American population-based sample, a proportion similar to our previously published data from a collection of cases.

VATER non-random association of congenital malformations: study based on data from four malformation registers

This study was undertaken to find a strict, unbiased epidemiological delineation of the VATER non-random association of congenital malformations and, based on registry information, to identify a group of probable VATER association infants suitable for etiological analyses. Information on 5,260 infants with multiple malformations was collected from four large registers of congenital malformations. Data were analyzed using a statistical method in which various putative confounders were controlled for. Our results indicate the existence of a distinct group of malformations corresponding to the VATER association: esophageal atresia, anal atresia, upper preaxial limb reduction defects, and costo-vertebral malformations. A subdivision into an upper and a lower group of VATER association was indicated, with heart malformations associated with the upper group and kidney malformations associated with the lower group. Restricting the inclusion criteria for VATER association to the above mentioned core malformations, few infants seem to belong to the VATER association, thus limiting the possibilities of carrying out etiological analyses. A relatively large number of infants may belong to a family of related conditions among which VATER association is a subgroup. In the search for risk factors, a strict definition of the VATER association is needed in order to not dilute the study material with irrelevant cases. The present study provides such strict inclusion criteria.

[ECLAMC: 30-year study of epidemiological surveillance of neural tube defects in Chile and Latin America]

BACKGROUND

There is an urgent need to assess the impact, on the incidence of neural tube defects, of the recently implanted flour fortification with folic acid in Chile. The Collaborative Study of Congenital Malformations in Latin America (ECLAMC) has carried out an uninterrupted register of congenital malformations in the last thirty years.

AIM

To assess the epidemiology of neural tube defects in Chile and determine the most adequate base period to evaluate the effects of Folic acid fortification.

MATERIAL AND METHODS

Analysis of ECLAMC database that has registered all births over 500 g from 1967.

RESULTS

From 1967 to 1999, there were 434.624 births in 18 hospitals in Chile and 3.586.569 births in 155 hospitals in the rest of Latin America. The rate of neural tube defects in Chile was 17.03 per 10.000, significantly higher than the rest of ECLAMC (14.88 per 10.000). The prevalence of neural tube defects has a statistically significant secular tendency to increase in the study period and is higher among stillbirths, newborns with a birth weight of less than 1500 g, women and offspring of mothers aged less than 19 years old.

CONCLUSIONS

The period 1982-1999 is considered the best period for reference comparisons of the effects folic acid supplementation.

Correlation between molecular and conventional genealogies in Aicuña: a rural population from Northwestern Argentina

Aicuña is a village in the northwest of Argentina, located about 300 km south of La Rioja city, in the province of La Rioja. The population of Aicuña derives from a founder couple established in the uninhabited Aicuña valley in the early years of the 17th century. Due to land ownership litigation, the descendants maintained a well-documented genealogy that extends for 12 generations, comprising more than 8,000 individuals. From the historical pedigree of Aicuña, we selected 14 males with direct patrilineal descent from the 2 most ancient male founders, and 23 donors (9 females and 14 males) with direct matrilineal descent from the most ancient female founder. All 3 founders lived in the 17th century. We collected DNA from buccal swabs and characterized the mitochondrial DNA (mtDNA) and Y haplotypes using 14 Y-specific markers, 11 mtDNA polymorphic markers and sequencing of the mt hypervariable regions 1 and 2. We found four different Y haplotypes: Y1 and Y2 haplotypes of European origin corresponding to the founder ancestors Francisco Páez de Espinoza and Apolinario Ormeño, which were shared by 6 and 3 donors, respectively. Three males selected as Ormeño patrilineal descendants showed a different Y haplotype (Y3), probably originated by erroneous paternity registration due to illegitimacy. The remaining case (haplotype Y4), also assumed to belong to the Ormeño lineage, was probably also due to an erroneously registered paternity. Twenty-two donors showed an association of mtDNA markers corresponding to the Amerindian haplotype A2. The founder of this matrilineage could be traced back for more than 14 generations. The haplotype B of one remaining female did not correspond with the historical pedigree and could be due to an error in the genealogy registration. Our results showed an 85% agreement between conventional and molecular genealogies, with mtDNA markers being Amerindian, and Y markers being European. The methodology used in this report is a tool which could potentially be employed as a precedent for land ownership by Aicuña villagers and Amerindian populations.

Consanguinity in South America: demographic aspects

A sample of 53,552 nonmalformed liveborn infants was ascertained by the Latin-American Collaborative Study of Congenital Malformations between 1967 and 1996. The mean consanguinity rate was 0.96%, with significantly higher values in Brazil and Venezuela, and lower in Argentina. Low paternal education and occupation levels were positively associated with consanguinity. First-cousin matings represented almost half of all consanguineous couples. The consanguinity was mainly of more closely related types in Brazil, while in Venezuela more remote types predominated. This could reflect differences in migration patterns and rates between these two countries.