A patient was diagnosed with isolated increase in LDL. His father and brother had the same disease with increased cholesterol. The likely diagnosis is:
**Core Concept**
The patient's condition, characterized by an isolated increase in low-density lipoprotein (LDL) cholesterol levels, is likely due to a genetic predisposition. This scenario suggests a familial pattern of inheritance, which points towards a specific genetic disorder affecting lipid metabolism.
**Why the Correct Answer is Right**
The patient's family history, with both his father and brother having the same disease, indicates an autosomal dominant pattern of inheritance. This is consistent with Familial Hypercholesterolemia (FH), a genetic disorder caused by mutations in the LDL receptor gene (LDLR) or the apolipoprotein B (APOB) gene. In FH, the LDL receptor is either non-functional or reduced in number, leading to impaired clearance of LDL cholesterol from the bloodstream, resulting in elevated levels.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the patient's condition, as Familial Combined Hyperlipidemia (FCH) is characterized by an increase in multiple lipid fractions, including LDL, triglycerides, and VLDL.
* **Option B:** This option is incorrect because Familial Dysbetalipoproteinemia (FD) is characterized by an increase in both IDL and VLDL, not just LDL.
* **Option C:** This option is not relevant to the patient's condition, as Sitosterolemia is a rare genetic disorder caused by mutations in the ABCG5 and ABCG8 genes, leading to increased levels of plant sterols.
**Clinical Pearl / High-Yield Fact**
Familial Hypercholesterolemia (FH) is a leading cause of premature cardiovascular disease, and early diagnosis and treatment are crucial to prevent cardiovascular events.
**Correct Answer: D. Familial Hypercholesterolemia (FH)**