🔑 Key Learning

  • MCTD = mixed features of SLE, systemic sclerosis & myositis + anti-U1-RNP
  • Relapsing polychondritis = recurrent inflammation of ear, nose, airways
  • FMF = AR condition causing polyserositis in patients of Mediterranean descent
  • Pseudoxanthoma elasticum = 'plucked chicken' skin changes + angioid streaks + CV/GI disease
  • AOSD = salmon rash + fevers + arthralgia + high ferritin, RF/ANA negative

🧬 Mixed Connective Tissue Disease (MCTD)

  • Features of SLE, systemic sclerosis, and myositis
  • Antibodies: Associated with anti-U1 ribonucleoprotein antibodies (Anti-RNP)

👀 Clinical Features

  • Myalgia
  • SOB from pulmonary hypertension
  • Polyarthralgia
  • Raynaud’s phenomenon
  • Dactylitis ("sausage fingers")
  • Rash
  • Oesophageal dysmotility
  • Renal/CNS involvement uncommon

💊 Management

  • DMARDs (e.g. methotrexate, hydroxychloroquine)

👂 Relapsing Polychondritis

  • Episodic inflammation of cartilage
  • Idiopathic or autoimmune

👀 Clinical Features

  • Auricular chondritis, vertigo, hearing loss
  • Nasal chondritis → saddle nose
  • Laryngotracheal → hoarseness, wheeze
  • Joint pain/arthralgia
Figure 225: Ear inflammation in a patient with relapsing polychondritis. John C. Starr et al., CC BY 3.0.

💊 Management

  • Steroids to induce remission
  • DMARDs for maintenance

🌊 Familial Mediterranean Fever

  • AR condition → recurrent polyserositis
  • Common in Turkish, Armenian, Arabic descent

👀 Clinical Features

  • Short attacks (1–3 days): fever, pleuritis, peritonitis, arthritis
  • Erysipeloid rash on legs
Figure 226: Patients with Familial Mediterranean Fever also present with erysipeloid skin rashes on the legs which mimic cellulitis. Dr. H.J. Lachman, CC BY 4.0.

💊 Management

  • 1st line: Colchicine

🐔 Pseudoxanthoma Elasticum

  • AR disorder due to mineralisation of elastic fibres

👀 Clinical Features

  • ‘Plucked chicken skin’ papules
  • Retinal angioid streaks
  • Intermittent claudication, IHD, mitral valve prolapse
  • GI bleeding (e.g. melaena)
Figure 226: Pseudoxanthoma elasticum of the posterior lateral neck. Note the characteristic 'plucked chicken appearance'. kilbad, CC BY 3.0.

          

🔥 Adult-Onset Still’s Disease (AOSD)

  • Autoimmune systemic condition of unknown cause

👀 Clinical Features

  • Triad: fever + joint pain + salmon-pink rash
  • Sore throat, lymphadenopathy, HSM, myalgia, pericarditis

🧪 Investigations

  • ↑ CRP, ESR, ferritin
  • ANA and RF usually negative

💊 Management

  • 1st line: NSAIDs ± corticosteroids
  • Long term: DMARDs (methotrexate)
  • Refractory: Anakinra (IL-1 receptor blocker)

📝 Exam Clues & Clinchers

  • Anti-U1-RNP → MCTD
  • Auricular chondritis + saddle nose → Relapsing polychondritis
  • Recurrent fever + serositis + Mediterranean ancestry → FMF
  • Angioid streaks + GI bleed + neck papules → Pseudoxanthoma elasticum
  • Fever + arthralgia + salmon rash + high ferritin → AOSD