Dermatology MCQ - Inflammatory Dermatoses - Systemic sclerosis diagnosis

A 55-year-old patient presents with Raynaud's phenomenon, puffy fingers, and gastroesophageal reflux disease. Physical examination reveals sclerodactyly and mat-like telangiectasias on the face. Which of the following additional findings would be sufficient for this patient to meet the 2013 ACR/EULAR classification criteria for systemic sclerosis?

A. A positive antinuclear antibody (ANA) test
B. The presence of digital pitting scars
C. A high-resolution CT scan showing bibasilar pulmonary fibrosis
D. A nailfold capillaroscopy showing capillary dropout and megacapillaries
E. A right heart catheterization confirming pulmonary arterial hypertension

Correct Answer: B. The presence of digital pitting scars

Explanation

The 2013 ACR/EULAR criteria for classifying systemic sclerosis (SSc) are weighted and points-based. A total score of ≥9 is needed to classify a patient as having SSc. The patient in the question already has several criteria:

• Skin thickening of the fingers (sclerodactyly): 4 points

• Raynaud's phenomenon: 3 points

• Telangiectasias: 2 points

• Current Total Score = 4 + 3 + 2 = 9 points.

Adding any other criterion from the list would increase the score, but it is already sufficient. However, the question asks for an additional finding that would be sufficient. Digital pitting scars are a standalone criterion worth 2 points, which would bring the total to 11 points, definitively classifying the patient.

Why other options are incorrect

• A. A positive antinuclear antibody (ANA) test: A positive ANA is very common in SSc (>90% of patients) but is not assigned any points in the 2013 criteria. It is not sufficient on its own to push a patient over the diagnostic threshold.

• C. A high-resolution CT scan showing bibasilar pulmonary fibrosis: Pulmonary fibrosis is a major complication but is not one of the classification criteria items. It is a consequence of the disease used for prognosis and management, not for initial classification.

• D. A nailfold capillaroscopy showing capillary dropout and megacapillaries: This is a very important finding that signifies the underlying microvasculopathy and is included in the criteria. A "scleroderma pattern" on nailfold capillaroscopy is worth 2 points. This would also be a correct answer, but the question asks for a single sufficient finding, and B is also correct and is a more direct clinical sign.

• E. A right heart catheterization confirming pulmonary arterial hypertension: Like pulmonary fibrosis, PAH is a severe complication but is not a classification criterion.

Key Associations for Systemic Sclerosis Diagnosis

• 2013 ACR/EULAR Classification Criteria: The maximum score is from skin thickening (9 points for thickening proximal to the MCP joints). Other items include:

  • Skin thickening of the fingers (puffy fingers=2 pts, sclerodactyly=4 pts)

  • Fingertip lesions (digital ulcers=2 pts, pitting scars=2 pts)

  • Telangiectasia (2 pts)

  • Abnormal nailfold capillaries (2 pts)

  • Raynaud's phenomenon (3 pts)

  • SSc-related autoantibodies (anti-centromere, anti-Scl-70, anti-RNA polymerase III: 3 pts)

• Role of Autoantibodies: Serology is critical for prognosis and subclassification, not just diagnosis.

  • Anti-Centromere: Limited cutaneous SSc, risk for PAH.

  • Anti-Scl-70 (Topoisomerase I): Diffuse cutaneous SSc, high risk for ILD.

  • Anti-RNA Polymerase III: Diffuse cutaneous SSc, high risk for scleroderma renal crisis and associated with rapid skin progression.

• Differential Diagnosis: Includes Morphea (localized scleroderma, no systemic involvement), Eosinophilic Fasciitis (no Raynaud's, "groove sign"), Scleredema (often post-infection, no Raynaud's), Nephrogenic Systemic Fibrosis, and Chronic Graft-versus-Host Disease.

• Diagnostic Approach: Diagnosis is clinical, supported by serology and nailfold capillaroscopy. The classification criteria are primarily for standardizing patients for research but are heavily used in clinical practice to confirm the diagnosis.