Which one of the following is the primary defect in pierre Robin syndrome?
**Core Concept**
Pierre Robin syndrome is a congenital anomaly characterized by micrognathia, glossoptosis, and upper airway obstruction. The primary defect in Pierre Robin syndrome involves a developmental abnormality of the mandible, which leads to a range of clinical manifestations. This condition is often associated with other anomalies, including cleft palate and cardiac defects.
**Why the Correct Answer is Right**
The primary defect in Pierre Robin syndrome involves a failure of the mandible to develop properly during fetal development. This is often due to a mutation in the genes responsible for the development of the first and second pharyngeal arches, which give rise to the jaw and surrounding structures. The abnormal development of the mandible leads to a range of clinical manifestations, including micrognathia, glossoptosis, and upper airway obstruction.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe the primary defect in Pierre Robin syndrome. While cleft palate is a common associated anomaly, it is not the primary defect.
* **Option B:** This option is incorrect because it is a secondary consequence of the primary defect in Pierre Robin syndrome, rather than the primary defect itself.
* **Option D:** This option is incorrect because it is a characteristic of the syndrome, rather than the primary defect.
**Clinical Pearl / High-Yield Fact**
Pierre Robin syndrome is often associated with other congenital anomalies, including cleft palate and cardiac defects. It is essential to recognize the clinical manifestations of this syndrome and perform a thorough evaluation to identify any associated anomalies.
**Correct Answer: C. Abnormal development of the mandible.**