## **Core Concept**
The patient's symptoms and radiographic findings suggest a diagnosis related to rheumatology, specifically a condition affecting the joints of the hands. The key features here are morning stiffness, aching hands, expansion at the base of the terminal phalanges, and tapering of the proximal phalanges.

## **Why the Correct Answer is Right**
The description provided matches **Psoriatic Arthritis (PsA)**, a form of seronegative spondyloarthropathy that can present with a variety of clinical features, including joint pain, stiffness, and swelling. The radiographic findings of expansion at the base of the terminal phalanges (suggestive of tufting) and tapering of the proximal phalanges are characteristic of PsA. PsA can cause significant morning stiffness and can lead to distinctive radiographic changes, including joint erosions, new bone formation, and changes in the terminal phalanges.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is not provided, but typically, conditions like Rheumatoid Arthritis (RA) could be considered. However, RA usually presents with symmetrical joint involvement, and while it can cause morning stiffness and erosive changes, the specific radiographic findings mentioned are more characteristic of PsA.
- **Option B:** Similarly, not provided, but if considering Osteoarthritis (OA), it's less likely given the description. OA can cause joint pain and stiffness but typically doesn't cause the specific radiographic changes described here, such as tapering of the proximal phalanges.
- **Option D:** Without specifics, it's hard to address directly, but conditions like Reactive Arthritis or Ankylosing Spondylitis might be considered in the differential for seronegative spondyloarthropathies. However, they usually have other distinctive features (e.g., conjunctivitis and urethritis for Reactive Arthritis, or back pain and sacroiliitis for Ankylosing Spondylitis) not mentioned here.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that **Psoriatic Arthritis can present with a variety of skin and joint manifestations**, and not all patients have psoriasis at the time of arthritis diagnosis. The presence of significant morning stiffness and distinctive radiographic changes, especially in a patient with possible skin psoriasis (not mentioned but relevant), should prompt consideration of PsA.

## **Correct Answer:** C.