Introduction: The Disorders of Sex Development (DSDs) may arise from various genetic disorders therefore cytogenetic studies are necessary to determine the chromosomal sex. The 45,X/46,XY karyotype is considered a mixed gonadal dysgenesis (MGD) and the mosaicism in this condition has a low incidence: 1.5 per 10 000 newborns, characterized by a broad phenotypic spectrum.
Objective: The aim of this report is to present a mexican newborn female patient with a phenotype of ambiguous genitalia and a mos 45,X/46XY karyotype. Product of the IV pregnancy, of non-consanguineous parents. Mother of 39 years and father of 42. They refer threatened abortion during the first trimester. Born at 37 weeks of gestation, normal delivery. At birth: weight 3500 gr, height 53 cm. Physical examination: dolichocephalism, low posterior implanted hair, narrow forhead, sparse eyebrows, hypertelorism, epicanthic folds; depressed nasal bridge, long philtrum, wide mouth, high arched palate; posteriorly rotated ears, narrow chest; genital shown micropenis, right and left hypoplasic gonads. Histopathological studies: right gonad 1.7×0.8 cm with histological evidence of testicular dysgenesis; left gonad 7×5 mm with histological data of testicular dysgenesis with fibrous band. Both were compatible with mixed gonadal dysgenesis. Cytogenetic analysis of peripheral blood lymphocytes revealed a karyotype with mos 45,X/47,XY with a 400 bands resolution level according to ISCN 2013.
Discussion: There are few Latin American cases reported in the literature with Mixed Gonadal Dysgenesis and a mos 45,X/46,XY karyotype. Cases of newborns with genital ambiguity occur most frequently in mosaicism 45,X/46,XY and this proportion should be correlated with the phenotype. Clinical features were recently reported in this patients including peculiar fascies, renal, cardiac and neurologic anomalies.
Conclussion: The Mixed Gonadal Dysgenesis includes congenital anomalies including citogenetic, gonadal and genital alterations. The mosaicism is rare and in this case all the results correspond to those reported in other literature. These cases require complete clinical examination, cytogenetic and histopathological findings, and the performance of new diagnostic methods such as screening of microdeletions in sexual chromosomes.