NBEO Systemic Disease Practice Exam 2026 - Free Systemic Disease Practice Questions and Study Guide

An XXY chromosome configuration is indicative of Klinefelter's syndrome, a genetic condition occurring in males. This syndrome results from the presence of an extra X chromosome, leading to a total of 47 chromosomes. The additional X chromosome disrupts normal male development, leading to various physical and developmental characteristics such as reduced testosterone levels, infertility, and often breast tissue development (gynecomastia).

Klinefelter's syndrome can also impact cognitive development to some extent, but it is primarily characterized by its specific physical manifestations and reproductive challenges. Individuals with this condition may not be diagnosed until adolescence or adulthood, especially if symptoms are mild.

In contrast, other conditions mentioned in the options arise from different chromosomal configurations. For instance, Turner syndrome involves a single X chromosome (45,X) in females, Down syndrome is caused by an extra copy of chromosome 21 (trisomy 21), and neurofibromatosis is a genetic disorder usually associated with mutations in specific genes rather than chromosomal number abnormalities. Thus, Klinefelter's syndrome uniquely aligns with the XXY configuration, making it the correct choice.