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Patient Case: Overlap Syndrome and Mixed Connective Tissue Disease

Patient Case: Overlap Syndrome and Mixed Connective Tissue Disease

Discussion

A 35-year-old female presents to a regional hospital with a three-year history of joint pain, muscle weakness, and persistent fatigue. She describes intermittent swelling and stiffness in her fingers, especially in the morning, along with difficulty gripping objects. Over the past year, she has noticed skin tightening over her hands and occasional bluish discoloration of her fingers in cold weather. She also reports episodes of shortness of breath and difficulty swallowing solid foods.

On examination, she has swollen and tender metacarpophalangeal (MCP) joints, mild skin thickening over the fingers, and puffy hands. There is mild weakness in her proximal muscles, and lung auscultation reveals fine bibasilar crackles. Laboratory tests show a positive antinuclear antibody (ANA) with high anti-U1 RNP antibody levels. Inflammatory markers (ESR and CRP) are mildly elevated, and creatine kinase (CK) is also elevated. A chest X-ray reveals interstitial lung changes.

A diagnosis of Mixed Connective Tissue Disease (MCTD) is made, given features overlapping systemic lupus erythematosus (SLE), systemic sclerosis, and polymyositis. The patient is started on corticosteroids and hydroxychloroquine, with a plan to introduce immunosuppressants. She is also referred to a rheumatologist for long-term management to monitor for disease progression and organ involvement.

Questions
1. What is the most likely diagnosis in this patient?

a) Rheumatoid arthritis

b) Mixed connective tissue disease (MCTD)

c) Systemic lupus erythematosus (SLE)

d) Sjögren’s syndrome

2. Which of the following laboratory findings is most characteristic of mixed connective tissue disease (MCTD)?

a) Positive anti-U1 RNP antibody

b) Positive anti-CCP antibody

c) Low vitamin D levels

d) Elevated uric acid levels

3. Which of the following organ systems is most commonly involved in MCTD?

a) Gastrointestinal system only

b) Kidneys only

c) Lungs, muscles, and joints

d) Nervous system exclusively

4. What is the most appropriate initial treatment for this patient?

a) Corticosteroids and immunosuppressants

b) Antibiotics and painkillers

c) Physical therapy alone

d) Surgical intervention

Reveal answers

Answers

1. b) Mixed connective tissue disease (MCTD)

The patient presents with overlapping features of systemic sclerosis (skin tightening, Raynaud’s phenomenon), polymyositis (muscle weakness, elevated CK), and lupus-like joint pain, which is characteristic of MCTD.

2. a) Positive anti-U1 RNP antibody

MCTD is strongly associated with anti-U1 RNP antibodies, which help differentiate it from other connective tissue diseases like SLE or systemic sclerosis.

3. c) Lungs, muscles, and joints

MCTD commonly affects the musculoskeletal system (arthritis, myositis), lungs (interstitial lung disease), and skin, making these systems key areas of concern.

4. a) Corticosteroids and immunosuppressants

Immunosuppressive therapy is crucial in managing MCTD to control inflammation, prevent organ damage, and manage symptoms effectively.