**Core Concept**
Arthritis mutilans is a rare and severe form of psoriatic arthritis characterized by destructive joint damage and deformities, leading to significant disability and loss of function. It occurs in patients with psoriasis and is often associated with severe disease activity.

**Why the Correct Answer is Right**
Arthritis mutilans is a subtype of psoriatic arthritis that is characterized by a sudden and severe inflammatory process that destroys the joints, leading to deformities and loss of function. This condition is often associated with marked inflammation, bone resorption, and joint fusion, resulting in severe disability. The exact pathophysiology of arthritis mutilans is not fully understood, but it is believed to involve a combination of genetic predisposition, immune system dysregulation, and environmental factors.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because arthritis mutilans is not seen in patients with rheumatoid arthritis; it is a distinct entity associated with psoriasis.

**Option B:** This option is incorrect because arthritis mutilans is not characterized by joint pain and stiffness; it is marked by destructive joint damage and deformities.

**Option C:** This option is incorrect because arthritis mutilans is not seen in patients with osteoarthritis; it is a distinct entity associated with psoriasis.

**Clinical Pearl / High-Yield Fact**
Arthritis mutilans is a medical emergency that requires prompt treatment to prevent further joint damage and deformities. Early recognition and intervention are crucial to improving outcomes and preventing long-term disability.

**Correct Answer:** D. Psoriatic arthritis