**Question:** A girl presents with primary amenorrhea, short stature, and widely spaced nipples. Karyotype of the girl would be:

A. 46 XX
B. 46 XY
C. 45,X
D. 47,XXX

**Core Concept:**

Primary amenorrhea refers to the absence of menarche (first menstrual period) by the expected age of onset. It can be due to various causes, including chromosomal abnormalities, endocrine disorders, and structural abnormalities. The four options provided represent the most common karyotypes in females and males.

**Why the Correct Answer is Right:**

In this case, the patient presents with primary amenorrhea, short stature, and widely spaced nipples, which are features consistent with Turner syndrome (45,X karyotype). Turner syndrome is caused by the partial or complete absence of one X chromosome. As a result of this chromosomal abnormality, females with Turner syndrome typically have short stature, webbed neck, low-set ears, and narrow thorax. The widely spaced nipples are a common feature in Turner syndrome, which is caused by the lack of the Müllerian ducts.

**Why Each Wrong Option is Incorrect:**

A. 46 XX (Correct answer) - This is the normal female karyotype, and the patient does not exhibit the clinical features associated with this condition.
B. 46 XY (Correct answer) - This is the normal male karyotype, and the patient does not exhibit the clinical features associated with this condition.
C. 45,XX (Correct answer) - This is the normal female karyotype, and the patient does not exhibit the clinical features associated with this condition.
D. 47,XXX (Correct answer) - This is the karyotype for a patient with three X chromosomes, which is not the case for the presented patient.

**Clinical Pearl:**

Turner syndrome is an example of a chromosomal disorder that can lead to primary amenorrhea, short stature, and other clinical features. Recognizing these features and understanding the relevant karyotype can guide the appropriate diagnosis and management of the patient. Additionally, it highlights the importance of considering chromosomal abnormalities in the differential diagnosis of girls with primary amenorrhea, even if the clinical features seem to point towards a hormonal or structural disorder.