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BACKGROUND: Differences in Sex Development (DSD) is a heterogeneous group of congenital alterations that affect inner and/or outer primary sex characters. Although these conditions do not represent a mortality risk, they can have a severe psycho-emotional impact if not appropriately managed. The genetic changes that can give rise to DSD are diverse, from chromosomal alterations to single base variants involved in the sexual development network. Epidemiological studies about DSD indicate a global frequency of 1:4500-5500, which can increase to 1:200-300, including isolated anatomical defects. To our knowledge, this study is the first to describe epidemiological and genetic features of DSD in a cohort of Mexican patients of a third-level care hospital. METHODS: Descriptive and retrospective cross-sectional study that analyzed DSD patients from 2015 to 2021 attended a Paediatric Hospital from Mexico City. RESULTS: One hundred one patients diagnosed with DSD were registered and grouped into different entities according to the Chicago consensus statement and the diagnosis defined by the multidisciplinary group. Of the total, 54% of them belong to the chromosomal DSD classification, 16% belongs to 46, XX and 30% of them belongs to the 46, XY classification. CONCLUSION: The frequency for chromosomal DSDs was consistent with the literature; however, we found that DSD 46, XY is more frequent in our cohort, which may be due to the age of the patients captured, the characteristics of our study population, or other causes that depend on the sample size.

RESUMEN

Introducción. El síndrome de Down es la causa genética más frecuente de discapacidad intelectual, con incidencia de 1/650 recién nacidos. La determinación de la variante citogenética es importante para el asesoramiento. En este trabajo se determinó la prevalencia de las variantes citogenéticas en los pacientes con síndrome de Down del Hospital General de México y se analizaron con relación a la edad materna. Métodos. Se revisaron los resultados de los cariotipos realizados por indicación de síndrome de Down de enero 1986 a diciembre 2010. Se obtuvieron las edades de los pacientes y de sus madres. Resultados. De 581 pacientes, 71 (12.22%) presentaron cariotipo normal. De los 510 confirmados para síndrome de Down, 445 (87.3%) resultaron con trisomía regular; 22 (6.3%), como producto de una translocación robertsoniana; y 43 (8.4%), mosaico. La edad materna en aquellos con trisomía regular (mediana de 30 años) y mosaicismo (mediana de 29 años) fue mayor que en los debidos a una translocación (mediana de 20 años). Conclusiones. Caracterizar la aberración cromosómica en pacientes mexicanos con síndrome de Down permitió dar un asesoramiento genético adecuado y establecer la prevalencia de mosaicismo en nuestra población, que resultó mayor a lo reportado en la literatura. Es importante detectar mosaicos en pacientes cuyos datos clínicos no confirmen síndrome de Down o presenten discapacidad intelectual de causa desconocida.

Background. Down syndrome is the principal genetic cause of learning disabilities, with an incidence of 1/650 live births. Diagnosis is confirmed by karyotyping. Chromosomal variants are important for genetic counseling. We determined the prevalence of cytogenetic variants in patients with clinically diagnosed Down syndrome in the Hospital General de México Dr. Eduardo Liceaga and discussed its relevance according to maternal age. Methods. We reviewed karyotype data of patients with clinically diagnosed Down syndrome from January 1986 to December 2010 and obtained maternal and patient ages. Results. From 581 patients analyzed, 71 (12.22%) had normal karyotype. In 510 patients we confirmed that 445 (87.3%) had a regular trisomy, 22 (6.3%) were the product of a Robertsonian translocation and mosaicism was found in 43 (8.4%) patients. Maternal age was higher in patients with regular trisomy (median: 30 years) and mosaicism (median: 29 years) than in those with translocations (median: 20 years). Conclusions. Characterization of chromosomal aberrations in Mexican DS patients allows us to offer appropriate genetic counseling and to establish the prevalence of mosaicism in our population, which was higher than the reported data. Cytogenetic analysis for detection of mosaicism is important in patients with scarce clinical data of DS or with learning disabilities of unknown origin.