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Sjogren syndrome

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Sjogren syndrome

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High Yield Notes
13 pages
Flashcards

Sjogren syndrome

15 flashcards
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USMLE® Step 1 style questions USMLE

3 questions
Preview

A 52-year-old woman comes to the physician complaining of pain during sexual intercouse for the last 2 months. She also has difficulty swallowing food, especially bread and crackers, and she needs to chew food for longer periods of time before swallowing it. The patient has no significant past medical history. Temperature is 37.3°C (99.1°F), pulse is 73/min, and blood pressure is 138/76 mmHg. Physical examination reveals diffuse, nontender enlargement of the parotid glands bilaterally. Oropharyngeal examination reveals multiple new dental caries and halitosis. Ophthalmologic examination reveals 20/40 visual acuity in both eyes. Laboratory studies reveal the following findings:
 

Laboratory value  Result
 Hemoglobin  10.2 g/dL 
 Hematocrit  31% 
 Platelet count  350,000/mm3 
 Leukocyte count  3,000/mm3 
 Erythrocyte sedimentation rate  52 mm/h 
 Antinuclear antibodies   Positive 
 Rheumatoid factor  Negative 
 Anti-dsDNA  Negative 
 Anti-Ro/La  Positive 
If this patient remains untreated, which of the following is she at increased risk of developing?

Transcript

Sjogren's syndrome, named after Dr. Henrik Sjogren who first identified it, is a common autoimmune disorder, typically occurring in women.

In Sjogren’s syndrome, the body’s immune cells go rogue and start attacking various exocrine glands, which are glands that pour their secretions into a duct; most commonly the salivary glands and the lacrimal, or tear, glands.

Normally, the cells of the immune system are ready to spot and destroy anything foreign pathogens that could cause the body harm.

Immune cells called antigen-presenting cells, which include macrophages and dendritic cells, latch onto pathogens and engulf them - literally swallowing them up.

Pieces of the pathogen called antigens are then presented on a major histocompatibility complex class II molecule, or MHC-class II molecule - which is like a serving platter for antigens. An antigen presenting cell then searches for a T cell that can bind to the antigen.

Once found, binding to the antigen helps activate this T cell, which then releases proinflammatory cytokines, or signaling molecules, that recruit more immune cells - ultimately leading to inflammation.

The exact cause for Sjogren's syndrome is unknown, but it seems to be related to both genetic and environmental factors.

Genetic factors include genes which code for specific types of MHC class II molecules, called human leukocyte antigen, or HLA genes. Specifically HLA- DRW52, HLA- DQA1, or HLA- DQB1.

Environmental factors include an infection of exocrine glands like the salivary and lacrimal glands. Infections can damage the cells of the salivary gland, and expose their cell components, including their DNA, RNA, and histones to circulating immune cells.

These cell components get picked up by antigen-presenting cells, and presented to T-cells. In individuals with Sjogren's syndrome, a T cell gets inappropriately activated by these nuclear components, and considers them to be foreign nuclear antigens.

The T-cells then activate B-cells, which start producing anti-nuclear antibodies, or ANAs, which are antibodies against the nuclear antigens.

Two types of ANA formed in Sjogren’s syndrome are anti- SS-A and anti- SS-B antibodies, which are formed against the ribonucleoproteins SS-A and SS-B.

Then, both T-cells and antibodies enter the circulation and reach the exocrine glands, where the T-cells secrete cytokines to recruit more immune cells and promote inflammation of the exocrine gland tissue.

Summary
Sjögren's syndrome is a chronic autoimmune disease in which the body's white blood cells destroy the moisture-producing glands of the body. This results primarily in the development of a dry mouth and dry eyes. Other symptoms can include dry skin, a chronic cough, vaginal dryness, numbness in the arms and legs, feeling tired, and muscle and joint pains.
Sources
  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Update in Sjögren syndrome" Current Opinion in Rheumatology (2000)
  6. "Novel autoantibodies in Sjögren's syndrome: A comprehensive review" Autoimmunity Reviews (2019)
  7. "Sjögren's syndrome" The Lancet (2005)