**Core Concept**
Kimmelstiel-Wilson nodules are a characteristic histopathological feature of diabetic nephropathy, a complication of long-standing diabetes mellitus. These nodules represent the earliest detectable changes in the kidney in response to high glucose levels.

**Why the Correct Answer is Right**
Kimmelstiel-Wilson nodules are formed due to the accumulation of mesangial matrix material, which is a result of the activation of the renin-angiotensin-aldosterone system (RAAS) and the increased synthesis of extracellular matrix proteins, such as collagen and laminin. The mesangial expansion and matrix deposition lead to the formation of nodular lesions in the glomeruli, which are then surrounded by a thickened glomerular basement membrane. The presence of Kimmelstiel-Wilson nodules is a hallmark of diabetic nephropathy and is often used as a diagnostic criterion.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Kimmelstiel-Wilson nodules are not typically associated with hypertension or primary glomerulonephritis.
**Option B:** This option is incorrect because while amyloidosis can cause glomerular damage, it does not typically result in the formation of Kimmelstiel-Wilson nodules.
**Option C:** This option is incorrect because focal segmental glomerulosclerosis (FSGS) is a different clinical entity that presents with a different histopathological pattern.

**Clinical Pearl / High-Yield Fact**
Kimmelstiel-Wilson nodules are often seen in patients with long-standing diabetes mellitus, and their presence is associated with a poor prognosis. Early detection and management of diabetes are crucial to prevent the progression of diabetic nephropathy.

**Correct Answer: D. Diabetic nephropathy.**