**Core Concept**
Familial hypercholesterolemia (FH) is a genetic disorder characterized by elevated levels of low-density lipoprotein (LDL) cholesterol due to mutations in the LDL receptor (LDLR) gene. This leads to impaired clearance of LDL particles from the bloodstream, resulting in hypercholesterolemia and increased risk of premature atherosclerotic cardiovascular disease.

**Why the Correct Answer is Right**
In FH, mutations in the LDLR gene disrupt the normal function of the LDL receptor, which is responsible for binding and internalizing LDL particles from the bloodstream. As a result, LDL particles accumulate in the blood, leading to hypercholesterolemia and increased levels of LDL cholesterol. The impaired clearance of LDL particles also leads to the accumulation of cholesterol in the arterial walls, contributing to the development of atherosclerosis.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the primary pathophysiology of familial hypercholesterolemia.
**Option B:** This option is incorrect because it refers to a different genetic disorder, familial combined hyperlipidemia, which is characterized by elevated levels of multiple lipoproteins, not just LDL cholesterol.
**Option C:** This option is incorrect because it describes a different condition, heterozygous familial hypercholesterolemia, which is a milder form of the disease and typically presents with lower levels of LDL cholesterol compared to homozygous FH.

**Clinical Pearl / High-Yield Fact**
The diagnosis of familial hypercholesterolemia is often delayed due to its similarity in presentation to other forms of hypercholesterolemia. A key distinguishing feature is the presence of tendon xanthomas, particularly in the Achilles tendons, which are a characteristic finding in patients with homozygous FH.

**Correct Answer: A. Familial hypercholesterolemia is a genetic disorder characterized by elevated levels of low-density lipoprotein (LDL) cholesterol due to mutations in the LDL receptor (LDLR) gene.**