USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

What is the most common karyotype in true hermaphroditism?

1. 46,XY

2. 46,XX

3. 47,XXY

4. 45,XO

The correct answer is: 46,XX

In true hermaphroditism, individuals possess both ovarian and testicular tissue, which can be influenced by their genetic background. The most common karyotype seen in cases of true hermaphroditism is 46,XX. This karyotype indicates the presence of two X chromosomes, which is typical for female development. In true hermaphrodites, despite having the chromosomal pattern associated with females, the presence of testicular tissue indicates that there may be a genetic anomaly or the influence of a Y chromosome gene, such as SRY (Sex-determining Region Y), which may have affected the development of the gonads. However, the presence of 46,XX suggests that hormonal influences or developmental anomalies led to the dual sexual characteristics seen in true hermaphroditism. Other karyotypes, such as 46,XY or 47,XXY, which may be seen in different disorders of sexual development, are less commonly associated with true hermaphroditism. The 45,XO karyotype, associated with Turner syndrome, is also not representative of true hermaphroditism, as it pertains typically to female characteristics without the coexistence of male gonadal tissue.