What physical exam finding in a 15-year-old boy would be concerning for delayed puberty?

The presence of small smooth testicles along with an absence of pubic or facial hair in a 15-year-old boy is indeed concerning for delayed puberty. During puberty, there is typically a noticeable development in secondary sexual characteristics, including testicular enlargement, the development of pubic and facial hair, and changes in voice.

Small, smooth testicles indicate that the boy is possibly in the prepubertal phase of development. In boys, the Tanner stages help define the progression of these changes, and the development of testicular size and texture is a key component of early pubertal signs. If the testicles remain small and smooth at age 15, without the growth of pubic or facial hair, it suggests that the boy may not have initiated puberty by the expected age range, which can indicate delayed puberty.

Assessing secondary sexual characteristics such as pubic hair is critical; the absence of these traits further supports concerns regarding normal pubertal progression. Thus, the combination of these findings aligns with clinical criteria for delayed puberty, making this choice the most concerning in the context given.