**Question:** True about Swyer's syndrome

A. It is a genetic disorder affecting both sexes equally.
B. It results in the absence of ovarian function, leading to primary amenorrhea and infertility in females.
C. It is a condition where the individual develops male characteristics but does not require treatment.
D. It is commonly associated with virilization in females, leading to masculinization of external genitalia.

**Correct Answer:** D. It is commonly associated with virilization in females, leading to masculinization of external genitalia.

**Core Concept:**
Swyer's syndrome, also known as pure gonadal dysgenesis, is a rare genetic disorder characterized by the absence of ovarian function in females. In this condition, the individual develops male reproductive characteristics due to incomplete development of the gonads (gonads are the primary reproductive organs in the body). The disorder primarily affects the gonadal development, leading to a lack of female hormones and the presence of male hormones.

**Why the Correct Answer is Right:**
Swyer's syndrome is caused by mutations in the SRY gene, which plays a crucial role in the development of the testes during fetal life. In this condition, the SRY gene fails to initiate testicular development, resulting in the absence of ovarian tissue and the presence of male genitalia. The male genitalia develop due to the excess production of male hormones, such as testosterone, which leads to the development of male secondary sexual characteristics.

**Why Each Wrong Option is Incorrect:**
A. The statement that Swyer's syndrome affects both sexes equally is incorrect. In reality, it predominantly affects females, but it can also affect males.
B. While ovarian dysfunction is present in Swyer's syndrome, virilization (masculinization of external genitalia) is primarily caused by the presence of male hormones like testosterone, not due to the absence of ovarian function.
C. Swyer's syndrome does not primarily result in the absence of external genitalia development in females. Instead, it leads to the development of male genitalia due to the production of male hormones.

**Clinical Pearl:**
Swyer's syndrome is essential for medical students to understand as it highlights the importance of SRY gene function in the development of male reproductive tissues and the consequences of its dysfunction. This knowledge helps in differentiating it from other conditions, such as Klinefelter syndrome, where the 22nd X chromosome is missing, leading to infertility and gynecomastia but no significant virilization of external genitalia.