**Core Concept**
The primary structural defect of an organ is a congenital anomaly that arises from an intrinsic abnormality in the development process. This defect is a result of an intrinsic problem during embryogenesis, which affects the formation of the organ.

**Why the Correct Answer is Right**
A malformation is a primary structural defect of an organ that results from an intrinsic abnormality in the development process. This can occur due to genetic mutations, chromosomal abnormalities, or environmental factors that affect the normal development of the organ. For example, a heart malformation can occur due to a genetic mutation affecting the development of the heart tube.

**Why Each Wrong Option is Incorrect**
**Option B:** Disruption refers to a secondary structural defect that occurs due to an external factor, such as a mechanical obstruction, that affects the normal development of an organ. This is not a primary structural defect.
**Option C:** Deformation refers to a secondary structural defect that occurs due to a mechanical force or pressure that affects the normal development of an organ. This is not a primary structural defect.
**Option D:** Association refers to a condition where two or more congenital anomalies occur together, but it is not a primary structural defect of an organ.

**Clinical Pearl / High-Yield Fact**
It's essential to differentiate between primary and secondary structural defects, as the underlying cause and treatment approach may differ.

**✓ Correct Answer: A. Malformation. A primary structural defect of an organ is termed a malformation.**