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PUK (Peripheral Ulcerative Keratitis) - Complete PG Exam Guide

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WHAT TO SAY FIRST (Examiner Hook)

"PUK is a potentially sight-threatening and life-threatening condition because it may be the first manifestation of a systemic vasculitis. Its detection mandates urgent systemic workup."

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1. DEFINITION

• Epithelial defect
• Stromal infiltration and thinning
• Associated limbal inflammation (limbitis/episcleritis/scleritis)

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2. PATHOGENESIS (Score Points Here)

1. Immune complex deposition in the peripheral cornea (the peripheral cornea is uniquely vulnerable due to proximity to limbal vasculature)
2. Episcleral and conjunctival capillary occlusion → cytokine release + inflammatory cell recruitment
3. Upregulation of collagenases (MMPs) + reduced activity of their inhibitors → stromal melting

Key point to say: "The peripheral cornea is a watershed area where immune complexes preferentially deposit, making it the battleground for systemic autoimmune disease."

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3. SYSTEMIC ASSOCIATIONS (Must Know in Order)

Examiner Tip: "Nearly 50% of patients with PUK have an associated systemic collagen vascular disease - RA is the most common." - Goldman-Cecil Medicine

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4. CLINICAL FEATURES

Symptoms

• Pain (prominent, may be severe)
• Photophobia
• Blurred vision
• Redness

Signs (slit-lamp findings to rattle off)

• Crescentic ulceration with epithelial defect at the limbus
• Stromal infiltration and thinning - peripheral
• Spread is circumferential (and occasionally central)
• No clear zone between the ulcer and the limbus (same as Mooren)
• Limbitis, episcleritis, or scleritis are usually present
• Scleral extension can occur - KEY differentiator from Mooren ulcer
• Advanced: "Contact lens cornea" - extreme thinning
• Advanced: Perforation

Special Variant - Rheumatoid PCUK

• Paracentral (not peripheral) location
• Punched-out lesion with little infiltrate
• In a quiet eye (no scleritis)
• Can perforate rapidly
• Responds well to topical ciclosporin ± bandage contact lens ± tissue glue
• Usually does NOT need systemic treatment

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5. PUK vs MOOREN ULCER - THE CLASSIC COMPARISON TABLE

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6. MOOREN ULCER (Know This to Compare)

• Definition: Rare, progressive circumferential peripheral stromal ulceration - idiopathic autoimmune
• Antigen: May represent host reaction to calgranulin C (hidden corneal antigen)
• Two types:
  • Type 1 (Benign): Older patients, unilateral, responds to medical therapy
  • Type 2 (Aggressive): Younger patients, bilateral, South Asian men, severe pain, needs systemic immunosuppression
• Hallmark sign: Undermined and infiltrated leading edge
• Vascularization occurs up to (but NOT beyond) the leading edge
• No scleritis (this is key - if scleritis is present, think systemic PUK)
• HCV association - Mooren-like ulcer associated with hepatitis C

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7. WORKUP (Demonstrate Systematic Approach)

History

• Connective tissue disease symptoms (joint pain, skin rash, oral ulcers)
• Contact lens use
• Prior HSV/VZV keratitis
• Inflammatory bowel disease
• Prior ocular surgery

Investigations

• Slit-lamp examination (infiltrate, epithelial defect, AC reaction, scleritis)
• Corneal sensation (rule out neurotrophic)
• Schirmer test (dry eye)
• Corneal scrapings + cultures (rule out infection first!)
• Dilated fundus exam (cotton-wool spots = connective tissue disease; posterior scleritis signs)

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8. TREATMENT

Step-by-step approach to impress examiner:

"PUK is caused by infection until proven otherwise." - Kanski's (This line scores marks)

• Preservative-free lubricants (artificial tears)
• Topical antibiotic prophylaxis if epithelial defect present (e.g., erythromycin ointment)
• Cycloplegic (cyclopentolate 1% or atropine 1%) if AC reaction or pain present
• Protective glasses (polycarbonate) during day; eye shield at night

• Doxycycline 100 mg OD or BD - for anticollagenase (MMP inhibitor) effect
• Ascorbic acid (Vitamin C) 1-2 g/day - collagen synthesis promoter

• Systemic steroids (prednisone 60-100 mg/day) - for acute control; pulsed IV for severe disease
• Add antiulcer prophylaxis (pantoprazole 40 mg or ranitidine 150 mg BD)
• Steroid-sparing agents for long-term:
  • Methotrexate, mycophenolate mofetil, azathioprine
  • Cyclophosphamide (especially for GPA)
  • Infliximab, Rituximab (biologics - "show promise")
• Always coordinate with rheumatologist

• Topical cyclosporin A (up to 2%) - takes weeks to work
• Tacrolimus 0.1% ointment - for refractory cases

"Topical steroids should be used with CAUTION or generally AVOIDED in PUK because they can worsen corneal thinning and risk perforation. The notable EXCEPTION is relapsing polychondritis where topical steroids may actually improve the thinning."

• Conjunctival resection/recession if no response to medical therapy (extends 4 mm from limbus, 2 mm beyond margins)
• Keratoepithelioplasty - donor corneal lenticule sutured onto scleral bed as physical barrier
• Cyanoacrylate tissue adhesive - impending/actual perforation
• Amniotic membrane graft - impending perforation
• Lamellar or penetrating keratoplasty - visual rehabilitation once inflammation settles (with immunosuppressive cover)

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9. DIFFERENTIAL DIAGNOSIS OF PERIPHERAL CORNEAL THINNING

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10. HIGH-YIELD EXAMINER POINTS (Say These Verbatim)

1. "PUK may precede the onset of systemic features" - meaning the eye is the window to undiagnosed vasculitis
2. "PUK in a quiet eye with a punched-out paracentral lesion = Rheumatoid PCUK" - distinct entity, responds to topical ciclosporin
3. "Topical steroids are generally avoided in PUK - except in relapsing polychondritis"
4. "GPA (Wegener's) is the second most common cause, but ocular features are the PRESENTING feature in 50% of GPA cases"
5. "Nearly 50% of patients with PUK have a systemic collagen vascular disease"
6. "Doxycycline works by MMP inhibition, not by its antibiotic effect"

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11. CLINICAL PHOTOGRAPH

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12. HOW TO STRUCTURE YOUR ANSWER IN VIVA

1. Open with the life-threatening angle (systemic vasculitis)
2. Define it (crescentic peripheral ulceration)
3. Pathogenesis (immune complex → collagenase cascade)
4. Systemic associations in order (RA > GPA > PAN > RP > SLE)
5. Clinical features with the PUK vs Mooren comparison
6. Workup (infection first, then systemic)
7. Treatment (doxycycline + systemic immunosuppression, avoid topical steroids, biologics)
8. Surgical options (conjunctival resection → glue → keratoplasty)
9. End with the exception (relapsing polychondritis and topical steroids)

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