**Core Concept**
The question tests the ability to identify a common cause of acute joint pain, specifically a condition characterized by recurrent episodes of intense pain, swelling, and redness in the joints, often affecting the base of the big toe.

**Why the Correct Answer is Right**
Gout is a form of inflammatory arthritis caused by the deposition of monosodium urate crystals within the joints. This is a result of hyperuricemia, which can be due to increased production of uric acid or decreased excretion. The deposition of urate crystals triggers an intense inflammatory response, leading to the characteristic symptoms of gout, including sudden onset of pain, swelling, and redness in the affected joint. The X-ray finding of soft tissue swelling is consistent with gout, as it shows the accumulation of fluid in the joint space.

**Why Each Wrong Option is Incorrect**
**Option B:** Parathyroid adenoma, also known as primary hyperparathyroidism, can cause hypercalcemia, which may lead to bone resorption and osteoporosis. However, it is not directly associated with joint pain or soft tissue swelling in the joints.

**Option C:** Psoriasis is a chronic skin condition characterized by thick, scaly patches on the skin, but it can also cause joint inflammation, known as psoriatic arthritis. However, psoriatic arthritis typically presents with a different set of symptoms, including joint stiffness, swelling, and pain, often in a more asymmetrical pattern.

**Option D:** Rheumatoid Arthritis (RA) is an autoimmune disease that causes chronic inflammation and pain in the joints, often leading to joint deformity and disability. While RA can cause joint pain and swelling, the presentation is typically more chronic and symmetrical, and the X-ray findings would show joint erosions and narrowing of the joint space.

**Clinical Pearl / High-Yield Fact**
Gout is often referred to as "the disease of kings" due to its historical association with excessive uric acid production, which can be caused by a diet rich in meat, seafood, and alcohol.

**✓ Correct Answer: A. Gout**