Dermatology MCQ - Inflammatory Dermatoses - Rheumatoid arthritis

A 68-year-old woman with a long-standing, seropositive rheumatoid arthritis presents with a 2-day history of painful, violaceous, purpuric papules and nodules on the pads of her fingers and the heels of her palms. Some of the lesions have small, central ulcers. Which of the following is the most likely diagnosis?

A. Gottron's Papules
B. Rheumatoid Nodules
C. Rheumatoid Vasculitis
D. Calcinosis Cutis
E. Osler's Nodes

Correct Answer: C. Rheumatoid Vasculitis

Explanation

This presentation is classic for rheumatoid vasculitis, which is a serious extra-articular complication of RA, typically occurring in patients with long-standing, severe, seropositive disease.

• Clinical Presentation: Rheumatoid vasculitis is a form of leukocytoclastic vasculitis that affects small-to-medium-sized vessels. The description of painful, purpuric papules and nodules on the fingertips (digital pulp) and palms is highly characteristic. These lesions can infarct, leading to the observed small, central ulcers. This is often referred to as "by-the-book" vasculitis or digital arteritis.

Why other options are incorrect

• A. Gottron's Papules: These are violaceous, flat-topped papules located over the metacarpophalangeal (MCP) and interphalangeal (IP) joints, which is the pathognomonic cutaneous sign of dermatomyositis. The location in this case (pads of fingers, heels of palms) is incorrect for Gottron's papules.

• B. Rheumatoid Nodules: These are the most common cutaneous feature of RA, presenting as firm, non-tender, subcutaneous nodules located over pressure points (e.g., elbows, forearms). They are not typically painful, purpuric, or located on the finger pads, and they do not ulcerate unless traumatized.

• D. Calcinosis Cutis: This refers to the deposition of calcium salts in the skin, presenting as firm, white or yellowish papules or nodules that can ulcerate and extrude chalky material. It is a hallmark of CREST syndrome (limited systemic sclerosis) and dermatomyositis, not rheumatoid arthritis.

• E. Osler's Nodes: These are tender, subcutaneous, purplish nodules on the pads of the fingers and toes. They are a classic sign of infective endocarditis, not rheumatoid arthritis.

Key Dermatological Associations for Rheumatoid Arthritis

• Rheumatoid Nodules: As above, these are the hallmark skin finding. Their presence is associated with more severe disease and positive rheumatoid factor (RF) and/or anti-CCP antibodies.

• Rheumatoid Vasculitis: A serious complication indicating a poor prognosis. It can manifest as:

  • Digital lesions as described.

  • Palpable purpura on the lower extremities (leukocytoclastic vasculitis).

  • Periungual infarctions.

  • Larger, deeper ulcers on the lower legs.

• Neutrophilic Dermatoses:

  • Rheumatoid Neutrophilic Dermatosis: Rare eruption of urticarial or erythematous plaques and nodules, often on the extensor surfaces. Histology shows a dense dermal neutrophilic infiltrate without vasculitis.

  • Pyoderma Gangrenosum: Can be associated with RA, presenting with painful, rapidly enlarging ulcers with a characteristic undermined, violaceous border.

• Interstitial Granulomatous Dermatitis (IGD): Presents with linear, cord-like indurations ("rope sign") or erythematous plaques on the trunk and limbs. Histology shows a "palisaded granulomatous dermatitis."

• Management of Rheumatoid Vasculitis: This is a medical emergency and signifies a severe systemic disease flare. Treatment involves high-dose systemic corticosteroids and potent immunosuppressants such as cyclophosphamide, rituximab, or azathioprine.