A new born with 46XX has external genitalia of male, All the following are the possible cause except :
**Core Concept**
The development of external genitalia in a newborn is influenced by the presence or absence of androgens during fetal development. The presence of androgens leads to the formation of male external genitalia, while their absence or presence of anti-androgens results in female external genitalia. However, in some cases, the presence of androgens can lead to the development of ambiguous or male-like external genitalia in a genetically female individual.
**Why the Correct Answer is Right**
In a genetically female newborn with 46XX chromosomes, the presence of androgens during fetal development can lead to the formation of male or ambiguous external genitalia. This can occur due to various reasons such as congenital adrenal hyperplasia (CAH), androgen-secreting tumors, or exposure to androgens from the mother. In CAH, the enzyme 21-hydroxylase is deficient, leading to an accumulation of androgen precursors, which can stimulate the development of male external genitalia.
**Why Each Wrong Option is Incorrect**
**Option A:** Congenital adrenal hyperplasia (CAH) is a possible cause of ambiguous or male external genitalia in a genetically female newborn. This condition is characterized by a deficiency of the enzyme 21-hydroxylase, leading to an accumulation of androgen precursors.
**Option B:** Exposure to androgens from the mother is a possible cause of ambiguous or male external genitalia in a genetically female newborn. This can occur due to various reasons such as androgen-secreting tumors or the ingestion of androgenic substances.
**Option C:** Congenital adrenal hyperplasia (CAH) is a possible cause of ambiguous or male external genitalia in a genetically female newborn. This condition is characterized by a deficiency of the enzyme 21-hydroxylase, leading to an accumulation of androgen precursors.
**Option D:** A genetic mutation in the SRY gene is a possible cause of ambiguous or male external genitalia in a genetically female newborn. The SRY gene is responsible for the development of testes and the formation of male external genitalia.
**Clinical Pearl / High-Yield Fact**
A newborn with ambiguous external genitalia should be evaluated for congenital adrenal hyperplasia (CAH) and androgen-secreting tumors, as these conditions can lead to the development of male or ambiguous external genitalia in genetically female individuals.
**Correct Answer: D. A genetic mutation in the SRY gene is typically associated with the development of testes and male external genitalia in genetically male (46XY) individuals, not genetically female (46XX) individuals.**