8 year old boy is brought with c/o progressive weakness & difficulty getting up the shows the following finding what is the MC type of mutation leading to this condition?
**Core Concept**
The underlying condition described, characterized by progressive weakness and difficulty getting up, suggests a muscular dystrophy, likely Duchenne Muscular Dystrophy (DMD). This condition is associated with mutations in the **dystrophin gene**.
**Why the Correct Answer is Right**
The most common type of mutation leading to DMD is a **deletion mutation**. These mutations result in a frameshift, leading to a nonfunctional dystrophin protein. The **dystrophin gene** is located on the X chromosome, and mutations in this gene disrupt the production of dystrophin, a crucial protein for muscle function.
**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because while point mutations can occur, they are not the most common type of mutation in DMD.
**Option B:** This is also incorrect as duplications, though possible, are less frequent than deletions in DMD.
**Option C:** Similarly, this option is incorrect because, although possible, it is not the most common mutation type in DMD.
**Clinical Pearl / High-Yield Fact**
DMD is an X-linked recessive disorder, primarily affecting males. A key clinical feature is the Gower's sign, where patients use their hands to "walk" up their own body to stand up from a lying down position.
**Correct Answer:** D. Deletion mutation