## Distinguishing Limited vs. Diffuse Cutaneous Systemic Sclerosis ### Serological and Clinical Phenotypes **Key Point:** Anti-centromere antibodies (ACA) are strongly associated with limited cutaneous SSc (lcSSc), occurring in 70–80% of lcSSc cases. Anti-Scl-70 antibodies are associated with diffuse cutaneous SSc (dcSSc) and predict worse prognosis. ### Comparison Table | Feature | Limited Cutaneous SSc (lcSSc) | Diffuse Cutaneous SSc (dcSSc) | | --- | --- | --- | | **Skin involvement** | Distal to elbows/knees; face | Proximal; trunk; early face involvement | | **Anti-centromere antibodies (ACA)** | 70–80% | 5–10% | | **Anti-Scl-70 antibodies** | 5–10% | 40–60% | | **Onset of internal organ involvement** | Late (5–10 years) | Early (within 1–3 years) | | **Pulmonary fibrosis** | Rare | Common (50%) | | **Scleroderma renal crisis** | Rare (<2%) | Common (10–15%) | | **Prognosis** | Better; longer survival | Worse; higher mortality | | **CREST syndrome** | Classic presentation | Uncommon | ### High-Yield Mnemonic **Mnemonic:** **CREST** — **C**alcinosis, **R**aynaud phenomenon, **E**sophageal dysmotility, **S**clerodactyly, **T**elangiectasia. This syndrome is the hallmark of lcSSc and is associated with ACA positivity. ### Clinical Pearl **Clinical Pearl:** ACA-positive patients have a favorable long-term prognosis with slow progression and late-onset internal organ involvement. PAH (pulmonary arterial hypertension) is the most common internal organ manifestation in ACA-positive lcSSc, but it typically appears 5–10 years after disease onset, not within 1 year. ### Pathophysiology Anti-centromere antibodies target kinetochore proteins and are associated with a more indolent, limited form of disease. Anti-Scl-70 antibodies target topoisomerase I and correlate with aggressive fibrosis and early internal organ involvement.
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