**Question:** Tendon xanthomas are seen in -

A. Familial Hypercholesterolemia
B. Hypothyroidism
C. Hypothyroidism
D. Hypoparathyroidism

**Correct Answer:** A. Familial Hypercholesterolemia

**Core Concept:** Tendon xanthomas are a characteristic clinical sign in certain medical conditions. They are yellow, firm, and translucent lesions that appear on the tendons, particularly in the extensor surfaces of the hands and feet. These lesions are caused by the accumulation of cholesterol esters within macrophages, which results in lipid deposits in the dermis and subcutaneous tissue.

**Why the Correct Answer is Right:** Tendon xanthomas are primarily associated with high levels of low-density lipoprotein (LDL) cholesterol, a key component of familial hypercholesterolemia. Familial hypercholesterolemia is a genetic disorder characterized by elevated LDL cholesterol levels, increased cholesterol synthesis, and reduced LDL receptor activity. These factors lead to the accumulation of cholesterol in the skin and tendons, causing the formation of tendon xanthomas.

**Why Each Wrong Option is Incorrect:**

**A. Hypothyroidism:** Hypothyroidism results in decreased cholesterol synthesis and increased degradation of LDL particles. This leads to a decrease in LDL cholesterol levels and the absence of tendon xanthomas.

**B. Hypothyroidism:** Similar to option A, hypothyroidism causes a decrease in cholesterol synthesis and LDL cholesterol levels, leading to the absence of tendon xanthomas.

**C. Hypothyroidism:** As mentioned above, hypothyroidism results in lower cholesterol synthesis and LDL cholesterol levels, making it another incorrect option.

**Clinical Pearl:** Understanding the pathophysiology of tendon xanthomas allows physicians to make a correct diagnosis and initiate appropriate management strategies for patients presenting with these lesions. A thorough clinical examination, including palpation and visual assessment, is crucial in identifying such lesions, which may aid in establishing the diagnosis of familial hypercholesterolemia or other lipid disorders.