**Core Concept**
Multiple Endocrine Neoplasia type 2 (MEN-2) is a rare genetic disorder characterized by the development of medullary thyroid carcinoma, pheochromocytoma, and primary hyperparathyroidism. The condition is caused by mutations in the RET proto-oncogene, leading to the activation of the MAPK/ERK signaling pathway and subsequent tumor formation.

**Why the Correct Answer is Right**
MEN-2A is associated with medullary thyroid carcinoma, pheochromocytoma, and primary hyperparathyroidism, while MEN-2B is characterized by medullary thyroid carcinoma, pheochromocytoma, and mucosal neuromas. MEN-4, on the other hand, is a more heterogeneous condition that can present with a variety of endocrine abnormalities, including medullary thyroid carcinoma, but it is not typically associated with the characteristic triad seen in MEN-2A and MEN-2B.

**Why Each Wrong Option is Incorrect**
**Option A:** MEN-2A is a well-established subtype of MEN-2, so this option is incorrect.
**Option B:** MEN-2B is another recognized subtype of MEN-2, so this option is also incorrect.
**Option D:** MEN-4 can present with medullary thyroid carcinoma, but it is not a distinct subtype of MEN-2.

**Clinical Pearl / High-Yield Fact**
MEN-2 is typically inherited in an autosomal dominant pattern, and genetic testing for the RET proto-oncogene is available to identify carriers. Early diagnosis and prophylactic thyroidectomy can significantly improve outcomes for individuals with MEN-2.

**Correct Answer:** D. MEN-4.