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Sjögren’s Syndrome & Mixed CTD | MRCP Part 1

TL;DR

Sjögren’s Syndrome & Mixed CTD are high-yield rheumatology topics for MRCP Part 1, commonly tested through antibody profiles, systemic features, and complications. Focus on anti-Ro/La antibodies and lymphoma risk in Sjögren’s, and anti-U1 RNP with pulmonary hypertension in Mixed CTD. Questions often rely on subtle clinical clues rather than long stems.


Why this matters

In MRCP Part 1, rheumatology questions often test pattern recognition rather than recall alone. Sjögren’s Syndrome and Mixed Connective Tissue Disease (MCTD) are classic examples where understanding autoantibodies, overlap syndromes, and complications is essential to scoring well.

These conditions frequently appear in single-best-answer questions where one key clue (e.g. dry eyes or Raynaud’s) points to the diagnosis. For a broader roadmap, explore the MRCP Part 1 overview.


Core sections

1. Sjögren’s Syndrome: Definition and classification

Sjögren’s Syndrome is a chronic autoimmune disease characterised by lymphocytic infiltration of exocrine glands, leading to:

  • Reduced tear production

  • Reduced saliva secretion

Types:

  • Primary Sjögren’s – occurs independently

  • Secondary Sjögren’s – associated with conditions such as rheumatoid arthritis or SLE

2. Clinical features of Sjögren’s (high-yield)

  • Dry eyes → gritty sensation, photophobia

  • Dry mouth → difficulty swallowing dry food

  • Parotid gland enlargement

  • Dental caries (frequent exam clue)

  • Fatigue and arthralgia

Extraglandular features:

  • Interstitial lung disease

  • Renal involvement (distal renal tubular acidosis)

  • Peripheral neuropathy

3. Antibodies and investigations (Sjögren’s)

  • Anti-Ro (SSA) – most sensitive

  • Anti-La (SSB) – more specific

  • ANA positive

  • Rheumatoid factor often positive

Diagnostic tests:

  • Schirmer’s test → reduced tear production

  • Minor salivary gland (lip) biopsy → lymphocytic infiltration

Authoritative reference:

4. Complications of Sjögren’s (exam focus)

The most important complication is:

  • Non-Hodgkin B-cell lymphoma

Clues suggesting lymphoma:

  • Persistent parotid enlargement

  • Lymphadenopathy

  • Low complement levels

5. Mixed Connective Tissue Disease (MCTD): Overview

MCTD is an overlap autoimmune condition with features of:

  • Systemic lupus erythematosus

  • Systemic sclerosis

  • Polymyositis

Key antibody:

  • Anti-U1 RNP

Reference:

6. Clinical features of MCTD

  • Raynaud’s phenomenon (often earliest sign)

  • Puffy fingers / swollen hands

  • Myositis (proximal muscle weakness)

  • Oesophageal dysmotility

  • Pulmonary hypertension (major cause of mortality)

7. Sjögren’s vs MCTD: Key comparison

Feature

Sjögren’s Syndrome

Mixed CTD

Key antibodies

Anti-Ro, Anti-La

Anti-U1 RNP

Dryness

Prominent

Rare

Raynaud’s

Sometimes

Very common

Pulmonary hypertension

Rare

Common

Lymphoma risk

Increased

Not typical

8. Five most tested subtopics

  1. Anti-Ro vs Anti-La antibodies

  2. Lymphoma risk in Sjögren’s

  3. Anti-U1 RNP in MCTD

  4. Raynaud’s phenomenon as an early clue

  5. Pulmonary hypertension in MCTD

9. Five common exam traps

  1. Confusing Sjögren’s with SLE

  2. Forgetting RF positivity in Sjögren’s

  3. Missing lymphoma risk

  4. Mixing up antibody profiles (e.g. anti-dsDNA vs anti-U1 RNP)

  5. Overlooking pulmonary hypertension in MCTD

10. Rapid revision list (must-know points)

  1. Sjögren’s = dry eyes + dry mouth

  2. Anti-Ro = most sensitive marker

  3. Anti-La = more specific

  4. Dental caries = key clue

  5. Lymphoma = major complication

  6. MCTD = overlap syndrome

  7. Anti-U1 RNP = hallmark

  8. Raynaud’s = early feature

  9. Pulmonary hypertension = leading cause of death

Medical student revising Sjögren’s Syndrome and MCTD for MRCP Part 1 exam

Practical examples / mini-cases

Case: A 50-year-old woman presents with persistent dry eyes, difficulty eating dry food, and bilateral parotid swelling. Blood tests show ANA positivity and anti-Ro antibodies.

Question: What is the most important long-term complication?

Answer: Non-Hodgkin lymphoma

Explanation: Chronic B-cell activation in Sjögren’s increases the risk of lymphoma, especially in patients with persistent gland enlargement.


Common pitfalls (5 bullets)

  • Attributing dry mouth to medications without considering Sjögren’s

  • Ignoring parotid enlargement as a warning sign

  • Confusing overlap syndromes with isolated diseases

  • Missing pulmonary hypertension in MCTD

  • Over-relying on symptoms without checking antibody patterns


FAQs

1. What antibodies are seen in Sjögren’s Syndrome?

Anti-Ro (SSA) and Anti-La (SSB) are characteristic, with ANA and RF often positive.

2. What is the hallmark antibody in Mixed CTD?

Anti-U1 RNP is the defining antibody and frequently tested in MRCP Part 1.

3. Why is lymphoma associated with Sjögren’s?

Chronic immune stimulation leads to B-cell proliferation, increasing lymphoma risk.

4. What is the most important complication of MCTD?

Pulmonary hypertension is the leading cause of mortality.

5. How do you differentiate MCTD from SLE?

MCTD features anti-U1 RNP and Raynaud’s phenomenon, whereas SLE commonly shows anti-dsDNA and renal involvement.


Ready to start?

To consolidate your understanding of Sjögren’s Syndrome & Mixed CTD, practise regularly with Free MRCP MCQs and simulate exam conditions using a Start a mock test.

For structured preparation, visit the MRCP Part 1 overview and complement this topic with targeted sessions on [/lectures/].


Sources

 
 
 

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