USMLE® Step 1 style questions USMLE
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:
|Erythrocyte sedimentation rate||52 mm/h|
Contributors:Pauline Rowsome, BSc (Hons), Tanner Marshall, MS, Evan Debevec-McKenney, Jahnavi Narayanan, MBBS
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.
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.
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.
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