Rheumatologic Diseases
Systemic Lupus Erythematosus (SLE)
Multi-system autoimmune disease with autoantibody production. 10x more common in women.
Subtypes
Acute Cutaneous Lupus (Malar Rash)
Rash across nose, sparing nostril divider. Rash may also be generalized on body and skin between joints of fingers.
Chronic Cutaneous Lupus (Discoid)
High likelihood of scarring. These patients usually do not have systemic involvement.
Neonatal Lupus
Passive transfer of SSA/B antibodies across placenta. Dermatologic effects will go away shortly after birth, while cardiovascular effects can be more serious.
Key clinical features
Dermatological: UV sensitivity
Oral: Mouth ulcers
Nephritis: Major cause of morbidity
Cardiovascular: Lesions of valves, coronary artery disease, pericardial inflammation (serositis)
Pathology
Interface dermatitis is the inflammation between the dermis and epidermis. Also exhibits "full house" immunofluorescence, in which all florescent stained proteins are positive.
Leukopenia: Low WBC
Anemia: Low RBC
Thrombocytopenia
Low complement levels
Lab testing
Screening for Anti-Nuclear Antibodies (ANA) which is highly sensitive, but not very specific. Everyone with Lupus will be positive, but so will a bunch of people without.
Mechanisms
An increase in apoptosis plus slow clearance results in increased exposure to self-DNA via increased neutrophil apoptosis, which could result in autoimmunity. Additionally, failure of negative selection could contribute.
A change in immune cell population could be a cause. This might stem from increased TFH and Th17 and Th17, or decreased Treg and CD8. This results in increased infections.
There is also a cytokine profile unique to lupus, in which there is a high B cell activating factor, increasing survival of B cell antibodies.
Outcomes
The main mechanistic effect is that high complement activation leads to complement protein depletion.
Sjogren's syndrome
Autoimmune disease primarily affecting the exocrine organs. 10-20x more common in women.
Key clinical features
Oral: Defect in salivary glands leads to dry mouth, loss of pila on tongue, increased caries (tooth decay). Deficits in parotid glands leads to oral swelling.
Eyes: Defect in lacrimal glands leads to severe dry eyes.
10x higher risk of lymphoma development.
Scleroderma
Fibrosis of multiple tissues (especially of the skin).
Key clinical features
Vascular: Reynaud’s syndrome (vasoconstriction of digital arteries from cold or stress)
Nail beds: Sporadic dilation of capillaries and telangiectasias (superficial blood vessels blanche with pressure)
Fingertips: Ischemia and ulceration due to thickening of media and intima layers of vessel
Dermatologic: Fibrosis or thickening of skin, giving a waxy appearance
Pulmonary: Fibrosis and honeycombing of lungs
Histologically, it presents increased fibrosis/collagen deposition of dermis.
Mechanisms
Key autoantibody targets
- SCL-70 (topoisomerase)
- Centromere
- RNA Pol III