A child is below the third percentile for height. His growth velocity is normal, but chronologic age is more than skeletal age. The most likely diagnosis is:
**Core Concept**
The child's growth pattern suggests a delay in skeletal maturation, which may be caused by a disorder affecting growth hormone secretion, thyroid function, or other endocrine factors.
**Why the Correct Answer is Right**
The child's normal growth velocity but delayed skeletal age indicates a potential issue with growth hormone secretion or action. This is supported by the concept of growth hormone insensitivity, where the body's tissues do not respond adequately to growth hormone, leading to short stature despite normal growth rates. This condition can be caused by mutations in the growth hormone receptor gene or insulin-like growth factor-1 (IGF-1) gene.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not address the specific findings of normal growth velocity but delayed skeletal age. Turner syndrome typically presents with short stature, but growth velocity is often decreased.
**Option B:** This option is incorrect because it does not account for the child's normal growth velocity. Constitutional delay in growth and puberty is characterized by a delay in growth and puberty, but growth velocity is typically decreased.
**Option C:** This option is incorrect because it does not provide a clear link between the child's findings and the diagnosis. Growth hormone deficiency typically presents with decreased growth velocity.
**Clinical Pearl / High-Yield Fact**
In cases of growth delay, it's essential to assess both growth velocity and skeletal age to determine the underlying cause. A delay in skeletal age, as seen in this child, suggests a potential issue with growth hormone secretion or action.
**Correct Answer:** C. Growth hormone insensitivity.