Trisomy X in a patient with childhood-onset systemic lupus erythematosus.

Childhood-onset systemic lupus erythematosus (cSLE) is a rare, chronic and systemic autoimmune disease generally with a more severe clinical phenotype than the adult-onset SLE. In both conditions, it is known that females are predominantly affected; therefore, the possible overlap of SLE and sex chromosomal abnormalities has attracted attention. Our case report describe the clinical manifestations and immunological profile of a Brazilian female with cSLE and trisomy X. The 22 year-old patient, diagnosed with cSLE at age of 11, present some features related to 47, XXX, such as difficulties at school and communication, although this was not enough to investigate for chromosome abnormalities. Cytoscan HD array screening allowed the comprehensive diagnosis for this patient. We also characterized her ancestral composition, showing that she has 6.2% higher African component than the mean from health subjects from the same geographical area. This report reinforces the role of the X chromosome dose effect for sex bias in SLE, as well as the importance of African ancestry composition in cLES. It also throws lights upon the application of high-throughput molecular analysis in a large scale cohort can be useful to detect the impact of the genomic findings for more accurate epidemiological data.

Ancestry Informative Marker Panel to Estimate Population Stratification Using Genome-wide Human Array.

Case-control studies are a powerful strategy to identify candidate genes in complex diseases. In admixed populations, association studies can be affected by population stratification, leading to spurious genetic associations. Ancestry informative markers (AIMs) can be used to minimise this effect. The aim of this work was to select a set of AIMs to estimate population stratification in a Brazilian case-control study performed using a genome-wide array. A total of 345 single nucleotide polymorphism (SNP) AIMs, selected from the Cytoscan HD array and based on previously reported panels, was used to discriminate between European, African, and Amerindian populations. These SNP-AIMs were used to infer ancestry in systemic lupus erythematosus (SLE) patients (n = 23) and in healthy subjects (n = 110). Moderate population substructure was observed between SLE and control groups (Fst = 0.0113). Although patients and controls have shown a major European genomic contribution, significant differences in the European (P = 6.47 × 10-5 ) and African (P = 1.14 × 10-3 ) ancestries were detected between the two groups. We performed a two-step validation of the 345 SNP-AIMs panel estimating the ancestral contributions using a panel of 12 AIMs and approximately 70K SNPs from the array. Evaluation of population substructure in case-control studies, avoiding spurious genetic associations, can be performed using our panel of 345 SNP-AIMs.