**Core Concept:**
Achondroplasia is a form of skeletal dysplasia, a group of conditions characterized by abnormal bone growth and development. The underlying issue in achondroplasia is a mutation in the FGFR3 gene, which leads to increased bone growth inhibition. This results in short stature, wide face, and other skeletal abnormalities. When both parents are carriers of the mutated gene, their children have a 25% chance of inheriting the mutated gene, a 50% chance of being carriers like the parents, and a 25% chance of having a normal gene.

**Why the Correct Answer is Right:**
In this case, the correct answer is C: **25%**. This is because both parents are carriers of the mutated FGFR3 gene. When they have a child, there is a 1 in 4 (25%) chance that the child will inherit the mutated gene, leading to having achondroplasia.

**Why Each Wrong Option is Incorrect:**
A. 50% chance is incorrect because carriers do not have the disease; they only have a 25% chance of passing on the mutated gene.
B. 75% chance is incorrect as carriers do not have the disease and have only a 25% chance of passing on the mutated gene.
D. 100% chance is incorrect because achondroplasia is inherited from one affected parent, not both.

**Clinical Pearl:**
When assessing a family with a child affected by achondroplasia, it is essential to counsel the family about the inheritance pattern and the risks for future pregnancies. This helps them make informed decisions regarding future pregnancies and provides guidance on genetic testing options. Families should be informed about the 25% chance of having another child with achondroplasia, the 50% chance of having a child with no disease but carrying the mutated gene, and the 25% chance of having a child without the disease and without the mutated gene.