**Question:** Which one of the following is least likely to occur in late extra articular sero-positive rheumatoid arthritis?

A. Calcification of soft tissues
B. Vasculitis
C. Endocrinal disorders
D. Skin lesions

**Core Concept:** Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that primarily affects the joints, leading to joint swelling, pain, and impaired function. However, it can also involve other organs and systems, a phenomenon known as extra-articular manifestations. In this case, we are focusing on late extra articular manifestations of sero-positive rheumatoid arthritis (RA), where sero-positive refers to the presence of rheumatoid factor (RF) or anti-citrullinated peptide antibodies (ACPA) in the patient's serum.

**Why the Correct Answer is Right:** Late extra articular manifestations in sero-positive rheumatoid arthritis are usually associated with an active inflammatory process. The correct answer, D - Skin lesions, is less likely to occur in late extra articular sero-positive rheumatoid arthritis because skin lesions are more commonly associated with early disease or less severe disease activity. In late disease, the focus is typically on internal organ involvement, such as vasculitis and endocrinal disorders, rather than skin involvement.

**Why Each Wrong Option is Incorrect:**

A. Calcification of soft tissues - This refers to the deposition of calcium salts within soft tissues, a condition more commonly seen in degenerative joint diseases like osteoarthritis or in calcific tendonitis. While calcification can occur in rheumatoid arthritis, it is less likely to be a primary manifestation in late extra articular sero-positive rheumatoid arthritis.

B. Vasculitis - Vasculitis is an inflammation of blood vessels that can be a manifestation of rheumatoid arthritis, particularly in early disease or with active inflammation. In late extra articular sero-positive rheumatoid arthritis, vasculitis is less likely due to the focus on internal organ involvement and lower disease activity.

C. Endocrinal disorders - Endocrinal disorders are manifestations of rheumatoid arthritis affecting the endocrine system. While these can occur in rheumatoid arthritis, they are less likely in late extra articular sero-positive rheumatoid arthritis due to the focus on internal organ involvement and lower disease activity in this stage.

**Clinical Pearl:** The term "extra-articular" refers to manifestations of rheumatoid arthritis occurring outside the joints. The focus in late extra articular sero-positive rheumatoid arthritis is on internal organ involvement and lower disease activity, making skin lesions (option D) less likely compared to early disease or active inflammation. In this scenario, the options A, B, and C are less likely due to the focus on internal organ involvement and lower disease activity in late extra articular sero-positive rheumatoid arthritis.