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Introduction and Methods: In order to compare the magnetic resonance image characteristics of individuals belonging to pedigrees carrying the mutation E280A-PS1 associated to early onset Alzheimer disease, coming from Antioquia, Colombia, 78 individuals were studied. 47 of them were carriers of the mutation, 23 of those presented symptoms and 31 individuals being controls (non carriers of the mutation)., Results: In summary, significative differences were appreciated between symptomatic individuals and those asymptomatic. There was not significant difference between asymptomatic carriers and the controls. The presence of the perihippocampal fissure constituted a difference statistically significant between the symptomatic individuals and those carriers asymptomatic and between the symptomatic ones and the controls. The interuncal distance increased significantly was another difference between symptomatic and asymptomatic individuals and among symptomatic and control group. The lobar atrophy and the ventriculomegaly were found in symptomatic individuals and they correlate with the disorder graveness. There was not significance in the presence of infarcts and/or hippocampal hyperintensities., Conclusion: These results corroborate the statement that magnetic resonance image is very useful in the diagnosis and follow-up of individuals affected by early onset Alzheimer disease.

Introduction and Objective: In order to elucidate the genetic and environmental components involved in the susceptibility to develop attention deficit hyperactivity disorder (ADHD), a complex segregation analysis on nuclear families (n = 53) ascertained from affected probands belonging to Medellín, in the Antioquian State, Colombia, was performed., Methods and Results: Models of cohort effect (non-inheritance), multifactorial, recessive major gene, non-major gene component and non-transmission of major gene were rejected. Contrarily, dominant and codominant major gene models and non-multifactorial component could not be rejected. Thus, the better model fitting the data was that of the major gene (dominant/codominant). This major gene explains more than 99.99% of the ADHD phenotypic variance (value of heritability in the mixed model equal to 0.007%), which permit to assume a low aport of the environmental component to the phenotype ADHD. Gene frequency of the major gene was 3% in the general population of Antioquia and its penetrance was closed to 30%., Conclusion: Some cautions and aspects related to the bias of the interview and diagnosis of the parents are discussed.

Studies performed in subtropical populations have found significant association between the phenotype multiple sclerosis (MS) and the major histocompatibility complex (MHC). We present the results of a case-control study conducted on a tropical population (Antioquia, Colombia) in order to detect a possible association between MS and HLA DQalpha (HLA DQA1*) alleles. Forty chromosomes belonging to MS patients were compared to two sets of controls (40 and 910 chromosomes, respectively). The HLA DQA1*0101 and DQA1*0102 alleles were found in a significantly higher proportion among the cases than among the controls, whereas the HLA DQA1*0103 allele was found in a significantly lower proportion of the cases. These results suggest that the association of HLA DQA1*0101, DQA1*0102 and DQA1*0103 to the MS phenotype found in Caucasian subtropical populations remains in individuals with MS inhabiting the tropics. This finding could mean that the major genetic component associated to the MHC in subtropical populations is the same in the tropics.

Isoenzyme variability and evidence of genetic exchange were evaluated in 75 wild stocks of Trypanosoma cruzi obtained from different hosts from 5 geographical regions within the endemic area in Colombia. Cluster analysis of genetic variability was attempted. Thirty-three multilocus enzyme genotypes (clonets) were identified from 75 stocks, 27 of which clustered with zymodeme Z1 and 6 with zymodeme Z3. Two stocks isolated from human infections showed the potential risk to rural communities in Colombia. The stocks exhibited departures from Hardy-Weinberg expectations, including both fixed heterozygote and fixed homozygote demes, where both segregation and recombination were absent. To inspect for population subdivision that might falsely imply clonality in these stocks, Wright's F statistics were calculated. Theta values (Fst) were significantly different from 0 when 33 clonets, 27 Z1-like clonets, and 5 geographical subpopulations were compared; thus, a significant amount of divergence has occurred between and within them. In addition, linkage disequilibrium was detected for most possible pairwise comparisons of loci. In conclusion, the above results all support a scenario of long-term clonal evolution in Colombian sylvatic T. cruzi populations.

Objective and Methods: An experimental study about the predictions from the multifactorial threshold model created by Falconer is presented, assuming that this model may explain the genetic mechanisms underlying the family aggregation of idiopathic epilepsies., Results: We failed to confirm the following predictions from the falconer model: decreased prevalence of disease in relatives, proportional to decreased family links, and the order of birth effect. An heredity greater than 100% was calculated which is concordant with the presence of at least a locus with a major gen affect., Conclusion: Our results reject the multifactorial threshold effect and suggest the presence of a major gen or Mendelian effect. An analysis of complex segregation is suggested for future studies.

Objective and Methods: We have analyzed a set of multigenerational extended pedigrees ascertained from affected cases of idiopathic epilepsy in the Antioquian Neurologic Institute. All pedigrees show familial aggregation of several forms of non myoclonic idiopathic epilepsy. In a recent paper, we have demonstrated that generalized idiopathic epilepsy of the awakening type is better explained by the existence of a major gene. In this paper, we have explored by simulation techniques the usefulness of the bigger pedigrees for linkage analysis. By using simlink and taking into account the parameters of the major gene, we have estimated that total power of three families is approximately 100 million times favoring the linkage detection., Results and Conclusions: These analyses suggest that the major gene accounting by the susceptibility to develop generalized idiopathic epilepsy of the awakening type could be localized by typifying affected families belonging to the Paisa community from Antioquia, Colombia (Acta Neurol Colomb 1997; 13: 69-75).

Objectives: To characterize clinical features of a very large pedigree with early-onset Alzheimer disease (AD) in which all affected individuals carry the identical glutamic acid-to-alanine mutation at codon 280 in the presenilin-1 gene., Design: Clinical histories were obtained by patient and family interviews and through medical or civil records. Using standard diagnostic criteria, a case series of 128 individuals was identified, of which 6 have definitive (autopsy-proven) early-onset AD, 93 have probable early-onset AD, and 29 have possible early-onset AD., Setting: Community based in Antioquia, Colombia., Patients: A population-based sample in which all members of 5 extended families (nearly 3000 individuals) were surveyed. Criteria for inclusion required obtaining sufficient information to categorize the individual as affected., Main Outcome Measures: Age at onset, neuropsychological profile, neurologic history, and examination., Results: The patients had a mean age at onset of 46.8 years (range, 34-62 years). The average interval until death was 8 years. Headache was noted in affected individuals significantly more frequently than in those not affected. The most frequent presentation was memory loss followed by behavior and personality changes and progressive loss of language ability. In the final stages, gait disturbances, seizures, and myoclonus were frequent., Conclusions: Other than the early onset, this clinical phenotype is indistinguishable from sporadic AD except that affected individuals frequently complained of headache preceding and during the disease. Despite the uniform genetic basis for the disease, there was significant variability in the age at onset, suggesting an important role for environmental factors or genetic modifiers in determining the age at onset.

Background: The knowledge of the genic structure of a population is of great importance for evolutive studies., Aim: To estimate in a Chilean population sample from the low-middle and low socioeconomic strata of Santiago, haplotypes and allele frequencies for Gm and Km loci., Subjects and Methods: The sample included 460 controls of a case-control study of typhoid fever., Results: The G1m-G2m-G3m most frequent haplotypes were: za;..;g or 1,17;(-);21 = 0.4493;fn;b or 3;23;5,13 = 0.2522; f-,..;b or 3;(-);5,13 = 0.1389; zax;..;g or 1,2,17;(-);21 = 0.0685; za;..;b or 1,17;(-);5,13 = 0.0454; za;n;g or 1,17;23;21 = 0.0207; f;..;g or 3;(-);21 = 0.0129. The frequencies of Km alleles were 0.2391 and 0.7609 for Km1 and Km3 respectively., Conclusions: These frequencies are within those found in Amerindian and Caucasian populations as expected from the origin of the Chilean population. Gm haplotypes did not differ from Hardy-Weinberg equilibrium, while a significant lack of homozygous Km1/km1 was found in Km.

In an attempt to identify the possible role of major genes, multifactorial inheritance, and cohort effects in the susceptibility to idiopathic epilepsy with generalized tonic-clonic seizures of the awakening type (GTCS), complex segregation analysis was performed in 196 nuclear families ascertained through affected probands with idiopathic epilepsy with GTCS belonging to the Paisa community of Antioquia (Colombia). Models postulating no transmission, single major locus (dominant and recessive) only, and multifactorial component only, were rejected. Since the codominant single major locus model could not be rejected and models that assign no major locus to transmission, no polygenic component to transmission, and no transmission of the major effect were rejected, complex segregation analysis suggested that a major autosomal codominant allele together with a multifactorial component (mixed model) best explained clustering of idiopathic epilepsy with GTCS in families of the Paisa community. The deficit of transmission of heterozygotes (0.17) is compatible with the existence of epistasis acting on a major gene whose frequency was estimated to be 0.0211. Its transmission variance accounts for 81% of the susceptibility to idiopathic epilepsy with GTCS. The complementary variance (19%) is due to the polygenic component.

Gm and Km allotypes of immunoglobulins were determined in children with typhoid fever (Cases), in children without infectious diseases (Con-1), and in children with fever but no Salmonella in their blood or bone marrow (Con-2). Children were sampled from the urban population of Santiago; and they belonged to the low and low-middle socioeconomic strata. Cases had a higher frequency of [f;(-);b1,b3 or 3;(-);5,13] G1m, G2m, G3m haplotype than Con-1 and Con-2. Con-1 and Con-2 did not differ in their Gm haplotype or Km allele frequencies, but they differed in phenotype distribution. Con-1 deviated from Hardy-Weinberg equilibrium for Km due to a lack of Km 1-1 homozygotes. The relationship among these results, the ethnic origin of Chileans, and the differential susceptibility to typhoid fever are discussed.

Most Colombian populations stem from the admixture of Caucasians, Amerindians and Negroids. In the world, these two latter ethnical groups show a significantly higher prevalence of epilepsy than the former one. We tested the hypothesis that the high prevalence of idiopathic epilepsy with generalized tonic clonic seizures found in the Antioquian population (Paisas), from Colombia, is due to their possible joint Negroid and Amerindian ethnic components. We have previously demonstrated that inheritance is the principal factor for developing epilepsy in this community. Analyses of racial admixture, heterogeneity between populations, genetic distance, and phyletic relationships were performed among epileptic and non epileptic samples from the Antioquian community. Also Caucasians, Spaniards, Basques, Jews, Chileans, Negroids, Amerindians and Mongoloids were included in the analysis. Four highly polymorphic blood systems were used as genetic markers: RH, MNS, ABO and FY. They were chosen because of their high discriminant power in these ethnic groups. In the population affected with idiopathic epilepsy, the estimated Negroid and Amerindian rates of admixture were low (3% and 14%, respectively). Although, these degrees of admixture can be explained due to common ancestral origins, the estimated proportion of Amerindian admixture in the epileptic affected population, was significantly higher than the estimated for the Non affected Antioquian population. The latter finding is consistent with the analysis of heterogeneity between populations that discriminated epileptic population from non epileptic Antioquian population (p < 0.05). Epileptic and non epileptic Paisas clustered in topology with Caucasians, very close to Spaniards and Basques and highly distant from Negroids and Amerindians. Thus, far, the origin of the high prevalence of idiopathic epilepsy in the Antioquian (Paisa) population cannot be explained by the hypothetical joint Negroid and Amerindian ethnical admixture, but using additional genetic markers and other methods of racial estimation of admixture it is necessary to corroborate if the Amerindian admixture component is significantly higher in the epileptic population than in the non epileptic Paisa population.