18.5 Systemic Sclerosis & Scleroderma Renal Crisis

5. Systemic Sclerosis (Scleroderma)

Systemic sclerosis (SSc) is a multisystem disorder characterized by widespread microvascular obliterative vasculopathy, immune dysregulation, and excessive extracellular matrix (chiefly type I and III collagen) accumulation in skin and internal organs.

Subtypes: Limited Cutaneous vs. Diffuse Cutaneous SSc

Systemic sclerosis is classified based on the anatomical distribution of cutaneous fibrosis:

                         Systemic Sclerosis Classification
                                         |
     +-----------------------------------+-----------------------------------+
     |                                                                       |
1. Limited Cutaneous SSc (lcSSc / CREST)                            2. Diffuse Cutaneous SSc (dcSSc)
   - Skin: Distal to elbows/knees + face                              - Skin: Proximal limbs + trunk + face
   - Long history of Raynaud's (decades)                              - Rapid onset; early visceral failure
   - Anti-Centromere Antibodies (70-80%)                              - Anti-Scl-70 (Topoisomerase I) / Anti-RNA Pol III
   - Late Complication: Isolated Precapillary                         - Complications: Severe Interstitial Lung Disease,
     Pulmonary Arterial Hypertension (PAH)                              Scleroderma Renal Crisis (Emergency!)

Limited Cutaneous Systemic Sclerosis (lcSSc / CREST Syndrome)

• Skin Involvement: Restricted to areas distal to the elbows and distal to the knees, and the face (spares the trunk, upper arms, and thighs).
• Raynaud's Phenomenon: Often precedes skin sclerosis by decades. Microvascular cold-induced vasospasm exhibits classic triphasic color changes: white (pallor / digital ischaemia) -> blue (cyanosis / deoxygenation) -> red (rubor / reactive hyperemia).
• The CREST Acronym:
  • C — Calcinosis Cutis: Painful, hard subcutaneous deposits of calcium hydroxyapatite in fingers, hands, and pressure points; can ulcerate and extrude chalky white material.
  • R — Raynaud's Phenomenon: Severe, with risk of digital pitting scars and ischaemic gangrene.
  • E — Oesophageal Dysmotility: Smooth muscle atrophy and fibrosis of the lower two-thirds of the oesophagus, with incompetence of the lower oesophageal sphincter. Manifests as severe refractory gastro-oesophageal reflux disease (GERD), dysphagia, and aspiration. Gastric antral vascular ectasia (GAVE / "watermelon stomach") causes chronic occult GI bleeding.
  • S — Sclerodactyly: Thickening and tightening of the skin of the fingers, leading to tapering of digits, loss of normal skin creases, and fixed flexion contractures.
  • T — Telangiectasia: Distinctive, flat, polygonal "mat-like" vascular dilatations over the face, lips, oral mucosa, and palms.
• Diagnostic Serology: Anti-Centromere Antibodies (ACA) are present in 70–80% of patients (giving a discrete speckled nuclear pattern on IF); highly specific for limited SSc.
• Major Lethal Complication: Isolated Pulmonary Arterial Hypertension (PAH / WHO Group 1). Develops insidiously late in the disease course (often 10–20 years post-diagnosis) due to proliferative obliterative vasculopathy of pulmonary arterioles without parenchymal fibrosis. Screened annually with transthoracic echocardiography, serum NT-proBNP, and serial pulmonary function tests showing a disproportionate reduction in gas transfer (isolated low DLCO with preserved FVC). Gold-standard diagnosis requires right heart catheterization (mean pulmonary artery pressure > 20 mmHg with pulmonary capillary wedge pressure <= 15 mmHg and pulmonary vascular resistance >= 2 Wood units). Treated with endothelin receptor antagonists (bosentan, ambrisentan), PDE-5 inhibitors (sildenafil), and prostacyclin analogues.

Diffuse Cutaneous Systemic Sclerosis (dcSSc)

• Skin Involvement: Rapidly progressive, extensive skin sclerosis involving the trunk, abdomen, upper arms, and thighs, in addition to distal limbs and face. Associated with intense early pruritus and cutaneous hyperpigmentation with sparing of perifollicular skin ("salt-and-pepper" depigmentation).
• Early Visceral Organ Involvement:
  • Interstitial Lung Disease (ILD): Major cause of death in dcSSc. Histopathology shows non-specific interstitial pneumonia (NSIP) or UIP. Presents with progressive exertional dyspnoea and dry cough; chest auscultation reveals fine "Velcro" bibasilar crackles. High-resolution CT (HRCT) demonstrates ground-glass opacities, traction bronchiectasis, and lower-lobe fibrosis. Pulmonary function tests show a restrictive ventilatory defect (reduced FVC < 80% predicted) with reduced DLCO.
  • Cardiac Involvement: Patchy myocardial fibrosis predisposing to diastolic dysfunction, heart failure, and life-threatening ventricular arrhythmias.
• Diagnostic Serology:
  • Anti-Scl-70 (Anti-Topoisomerase I): Present in 30–40% of dcSSc patients; strongly associated with rapidly progressive diffuse skin thickening and severe interstitial lung disease.
  • Anti-RNA Polymerase III: Present in 15–20% of dcSSc patients; strongly associated with rapidly progressive extensive skin thickening and a massively heightened risk of Scleroderma Renal Crisis.

6. Scleroderma Renal Crisis (SRC)

Scleroderma renal crisis is a life-threatening medical emergency occurring in 10–15% of patients with diffuse cutaneous systemic sclerosis (most commonly within the first 4 years of diagnosis).

Pathophysiology & Corticosteroid Trigger

• Mechanism: Severe microvascular endothelial injury in renal arcuate and interlobular arteries leads to marked intimal proliferation, "onion-skin" hyperplastic arteriolosclerosis, and microthrombosis. The resulting severe cortical renal ischaemia triggers massive, unregulated hypersecretion of renin by the juxtaglomerular apparatus (hyperreninaemic renal crisis).
• High-Risk Precipitant: High-dose systemic corticosteroids (prednisolone > 15 mg/day) are a well-recognized direct trigger for SRC. Corticosteroids must be strictly avoided or used at the lowest possible dose in patients with diffuse SSc.
• Autoantibody Risk: Presence of anti-RNA polymerase III antibodies confers the highest risk.

Clinical Presentation

• Abrupt Onset of Severe Hypertension: Accelerated/malignant hypertension (typically systolic BP > 180 mmHg, diastolic BP > 110 mmHg; however, up to 10% may present with normotensive SRC, which carries an even worse prognosis).
• Rapidly Progressive Oliguric AKI: Sudden, precipitous decline in renal clearance.
• Hypertensive Encephalopathy & Cardiac Decompensation: Headache, papilloedema, visual disturbances, seizures, flash pulmonary oedema.
• Microangiopathic Haemolytic Anaemia (MAHA) & Thrombocytopenia: Mechanical fragmentation of red blood cells passing through narrowed, fibrin-occluded renal arterioles produces circulating schistocytes (helmet cells) on peripheral blood film, marked elevation of LDH, indirect hyperbilirubinaemia, undetectable haptoglobin, negative direct Coombs test, and secondary consumptive thrombocytopenia.
• Urinalysis: Mild proteinuria (usually < 2 g/24h) with microscopic haematuria and granular casts; broad nephrotic-range proteinuria is distinctly unusual.

Emergency Management

• TREATMENT OF CHOICE: Immediate emergency initiation of an ACE inhibitor, specifically oral captopril (short-acting, easily titrated, started at 6.25–12.5 mg every 8 hours and rapidly escalated to maximum doses of 50 mg three times daily).
• CRITICAL CLINICAL PEARL: ACE inhibitors must be aggressively titrated to normalize blood pressure EVEN IF THE SERUM CREATININE RISES INITIALLY. The transient rise in creatinine reflects reduced efferent arteriolar tone in the setting of underlying renal ischemia; failing to control the systemic hypertension results in irreversible bilateral renal cortical necrosis. Renal recovery is slow, frequently taking 12–24 months; up to 50% of patients requiring temporary haemodialysis can successfully discontinue dialysis if ACE inhibitors are continued indefinitely.