**Question:** Koenen's periungual fibromas are seen in > 50% of cases with –

A. Hyperthyroidism
B. Vitamin D deficiency
C. Hypothyroidism
D. Hyperparathyroidism

**Core Concept:** Koenen's periungual fibromas are benign fibroepithelial tumors that develop around the nails, and are associated with specific hormonal imbalances.

**Why the Correct Answer is Right:** Koenen's periungual fibromas are commonly seen in patients with hyperparathyroidism, as this condition leads to increased parathyroid hormone levels. Parathyroid hormone has several effects on the nail bed, leading to the formation of these tumors.

**Why Each Wrong Option is Incorrect:**

A. Hyperthyroidism (option A): This condition is characterized by high thyroid hormone levels, not parathyroid hormone. Therefore, hyperthyroidism is not the correct answer.

B. Vitamin D deficiency (option B): Although vitamin D deficiency can lead to bone abnormalities, it does not cause Koenen's periungual fibromas. Moreover, vitamin D deficiency is associated with rickets, not fibromas.

C. Hypothyroidism (option C): Hypothyroidism is characterized by low thyroid hormone levels, not parathyroid hormone levels. Hence, hypothyroidism is not the correct answer.

D. Hyperparathyroidism (correct answer D): As mentioned earlier, hyperparathyroidism leads to increased parathyroid hormone levels, which in turn causes Koenen's periungual fibromas.

**Clinical Pearl:** A thorough understanding of hormonal imbalances is crucial in recognizing and managing patients with Koenen's periungual fibromas. A high index of suspicion is required when evaluating patients with these tumors, especially in the context of clinical history, physical examination, and laboratory investigations.

**Correct Answer:** D. Hyperparathyroidism

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**Core Concept:** Hormonal imbalances, particularly hyperparathyroidism, play a significant role in the pathogenesis of Koenen's periungual fibromas. These benign tumors develop due to the direct effects of parathyroid hormone on the nail bed, leading to fibroepithelial proliferation.

**Why the Correct Answer is Right:** Hyperparathyroidism, characterized by elevated parathyroid hormone levels, is the correct answer as it leads to the development of Koenen's periungual fibromas.

**Why Each Wrong Option is Incorrect:**

A. Hyperthyroidism (option A): Unlike hyperparathyroidism, hyperthyroidism is characterized by elevated thyroid hormone levels, not parathyroid hormone. Therefore, hyperthyroidism is not the correct answer.

B. Vitamin D deficiency (option B): Vitamin D deficiency, while associated with rickets, does not directly cause Koenen's periungual fibromas. The development of these tumors is linked to parathyroid hormone, not vitamin