Question 5 - Bone Scan of the Hands: Full Answer

1. Abnormality Shown on the Bone Scan (2 marks)

• The wrists (carpal bones)
• The metacarpophalangeal (MCP) joints

2. Diagnosis (2 marks)

• Symmetrical distribution of joint involvement
• Proximal hand involvement (wrists and MCPs), which is the characteristic pattern of RA
• Presentation with pain and swelling in wrists and fingers

• Sero-negative arthritis / psoriatic arthritis: tend to involve distal interphalangeal (DIP) joints
• Osteoarthritis: also involves distal joints, typically asymmetrical early on
• Gout: asymmetrical, often monoarticular initially

3. Typical Findings on Plain Radiographs in RA - List 3 (2 marks, any 3)

1. Periarticular osteopenia - loss of bone density immediately around the affected joints (especially at MCPs and wrists); this is one of the earliest radiographic signs
2. Marginal bone erosions - erosions at the bare area (exposed bone between articular cartilage and joint capsule), classically affecting the metacarpal heads and carpal bones, with no associated new bone formation (unlike sero-negative arthritis)
3. Symmetrical joint space narrowing - uniform loss of cartilage at affected joints due to pannus formation

• Soft tissue swelling around affected joints
• Subluxation / joint malalignment (ulnar deviation of fingers at MCPs)
• Bony ankylosis (late-stage disease)

• Grainger & Allison's Diagnostic Radiology - Distribution of Joint Involvement; Bone Changes (p. 1111-1112)
• Firestein & Kelley's Textbook of Rheumatology - Imaging section

Question 6 - 36-Year-Old Post-Splenectomy Man: Full Answer

1. What Does the Slide Show? (2 marks)

• Howell-Jolly bodies - small dark nuclear remnants within red blood cells (normally removed by the spleen)
• Target cells (codocytes) - RBCs with a central dense spot and peripheral ring of haemoglobin
• These two findings together are the hallmark of hyposplenism / functional asplenia following splenectomy

2. What Is the Diagnosis? (3 marks)

• Splenectomy 7 years ago - the risk of OPSI is greatest in the first 2 years but persists lifelong
• Loss of splenic macrophages, diminished tuftsin production, and loss of reticuloendothelial screening means encapsulated bacteria cannot be adequately cleared from the bloodstream
• With MPS negative, malaria is excluded; the fever + nausea + abdominal pain + elevated WCC in an asplenic patient = OPSI until proven otherwise

3. What Is the Specific Treatment? (6 marks)

1. Blood cultures - collect BEFORE starting antibiotics, but do not delay treatment waiting for results
2. IV broad-spectrum antibiotics immediately:
   • Vancomycin - broad Gram-positive cover including penicillin-resistant S. pneumoniae
   • Ceftriaxone - added for Gram-negative cover (N. meningitidis, H. influenzae)
3. Sepsis resuscitation - IV fluids, goal-directed therapy, ICU if required

1. Vaccination against encapsulated bacteria (ideally given 2 weeks before elective splenectomy, or given after emergency splenectomy):
   • Pneumococcal vaccine (S. pneumoniae)
   • Haemophilus influenzae type B vaccine
   • Meningococcal vaccine
   • Annual influenza vaccine
2. Prophylactic antibiotics - lifelong daily penicillin (or amoxicillin) prophylaxis, especially for the first 5 years post-splenectomy and in children until at least age 5
3. Patient education:
   • Wear a medical alert bracelet
   • Carry a laminated medical alert card and a letter with empiric antibiotic instructions
   • Keep a 5-day standby antibiotic supply, especially when travelling
   • Present to hospital immediately at the first sign of fever or infection

• Schwartz's Principles of Surgery, 11th Ed - "Antibiotics and the Asplenic Patient"; "OPSI Clinical Features"
• Current Surgical Therapy, 14th Ed - "Vaccination" (post-splenectomy section)
• Goldman-Cecil Medicine - Table 143-4: Incidental but Clinically Relevant Blood Smear Observations

Extra-GI Manifestations of Crohn's Disease

Key Concept: Activity-Dependent vs. Independent EIMs

1. Musculoskeletal (most common EIM category)

• Type 1 - Pauciarticular (<5 joints): parallels bowel disease activity; typically large joints (knees, ankles); nondeforming; rheumatoid factor negative
• Type 2 - Polyarticular (>5 joints): independent of bowel activity; often small joints (MCP, PIP); may persist for years

• Sacroiliitis - prevalence ~10%; bilateral and symmetrical; most common axial manifestation; may be asymptomatic
• Ankylosing spondylitis - prevalence ~3%; insidious low back pain + morning stiffness, improves with exercise; HLA-B27 positive in up to 75% of Crohn's patients with spondylitis; runs a course independent of bowel disease

• Osteopenia / osteoporosis (fracture risk 40% higher than controls) - multifactorial: steroid use, calcium/vitamin D malabsorption, proinflammatory cytokines (TNF), low BMI
• Sarcopenia - reduced muscle mass, seen in up to 60% of CD patients

2. Mucocutaneous

• Erythema nodosum (EN) - tender erythematous/dusky subcutaneous nodules, classically on the pretibial region; more common in women; tracks bowel activity; heals without scarring if not biopsied; strongly associated with arthropathy
• Pyoderma gangrenosum (PG) - starts as papule/pustule, progresses to deep ulcer with violaceous (purple) undermined borders and cribriform scarring; most often on the leg or periostomal; shows pathergy (enlarges with minor trauma); often occurs without a bowel flare in CD
• Oral aphthous stomatitis - most cephalad GI manifestation; can progress to labial swelling, angular cheilitis, mucosal cobblestoning (direct granulomatous involvement)
• Metastatic Crohn's (rare) - granulomatous skin lesions remote from the GI tract, histologically identical to the intestinal lesion
• Rare: leukocytoclastic vasculitis, Sweet syndrome (neutrophilic dermatosis), cutaneous polyarteritis nodosa, epidermolysis bullosa acquisita, psoriasis

3. Ocular

• Episcleritis - injection of the sclera/conjunctiva; more common in CD than UC; tracks bowel activity; relatively mild, usually self-limiting
• Anterior uveitis (iritis) - pain, photophobia, blurred vision; more serious; can occur independent of bowel activity; associated with HLA-B27 and spondylitis
• Rare: scleritis, keratopathy, night blindness (vitamin A malabsorption)

4. Hepatobiliary

• Cholelithiasis - prevalence 11-34%; ~twice the general population rate; ileal disease/resection impairs bile salt absorption → cholesterol stone formation; pigment stones also occur
• Primary sclerosing cholangitis (PSC) - prevalence 1.2-3.4% in CD; affects small biliary radicals; presents with abnormal LFTs; independent of bowel activity; major risk factor for cholangiocarcinoma
• Fatty liver (NAFLD) - ~23% of IBD patients
• Also: autoimmune hepatitis, pericholangitis, hepatic amyloidosis (<1%), pyogenic liver abscess, pancreatitis (idiopathic, autoimmune, or drug-induced e.g. thiopurines)

5. Renal / Genitourinary

• Nephrolithiasis - two types:
  • Calcium oxalate stones - fat malabsorption → free fatty acids bind luminal calcium → oxalate not cleared → hyperoxaluria (most common in CD with ileal disease)
  • Uric acid stones - from volume depletion and hypermetabolic state
• Rare: membranous nephropathy, glomerulonephritis, renal amyloidosis, interstitial nephritis (mesalamine-related)

6. Vascular / Haematologic

• Venous thromboembolism (VTE) - significantly increased risk; due to prothrombotic state (thrombocytosis, elevated fibrinogen, factor V/VIII, reduced antithrombin III and protein S)
• Arterial thrombosis (rare)
• Anaemia - multifactorial: iron deficiency (blood loss), B12 deficiency (terminal ileal disease/resection), anaemia of chronic disease
• Amyloidosis (systemic AA amyloidosis, rare)

7. Respiratory / Cardiac (rare)

• Asthma, COPD association (shared inflammatory pathways)
• Pericarditis, pleuritis

Growth Retardation (Paediatric)

• Nearly half of children with CD show subnormal height velocity; ~25% develop short stature; results from malnutrition + systemic inflammation; surgical resection often improves growth

• Sleisenger & Fordtran's Gastrointestinal and Liver Disease - Table 115.2 + EIM sections (pp. 2309-2311)
• Fischer's Mastery of Surgery, 8th Ed - Extraintestinal Manifestations of Crohn Disease
• Sabiston Textbook of Surgery - Clinical Presentation (p. 2087)
• Robbins & Kumar Basic Pathology