Approach To Hypersensitivity Flashcards
Type I Immediate Hypersensitivity
Step 1: Antigen exposure
Step 2: IgE cross-linking on mast cell
Step 3: Histamine, leukotriene, prostaglandin, tryptase release
Step 4: Symptoms of urticaria, rhinitis, wheezing, diarrhea, vomiting, hypotension, and anaphylaxis within minutes of exposure
Type II Cytotoxic Hypersensitivity
IgM or IgG Ab destroys cells by:
- obsonization
- complement mediated lysis
- Ab-dependent cellular cytotoxicity
Examples of Type II hypersensitivity
ABO mismatch
Graves Disease
Myasthenia Gravis
Type III Hypersensitivity
Step 1: Ag-Ab complex
Step 2: Complex active complement, neutrophils invade
Step 3: tissue inflammation (Tumor, Rubor, Calor, Dolor)
Examples of Type III hypersensitivity?
Systemic Lupus erythematosus
Rheumatoid Arthritis
Farmer’s Lung
6yo boy comes in early spring with rhinitis and sneezing for past week. What type of hypersensitivity?
Type I
-pollen allergy, mediated by histamine
25 yo female comes in with fatigue, blurry vision. She has ptosis and progessive muscle weakness. What type of hypersensitivity?
Type II
-due to IgM or IgG Ab destruction
58 yo male presents in afternoon w fever, chills, cough, chest tightness, and SOB. He had no signs this morning. Crackles are heard upon auscultation. What type of hypersensitivity?
Type III (farmers lung) -immune complexes depositing, neutrophils invading (fever, chills)
Type IV Cell mediated hypersensitivity
Delayed type
Step 1: Ag exposure sensitized cells
Step 2: T Cell activation 48-96 hours later
Examples of Type IV hypersensitivity
Poison Ivy, PPD testing for TB
12 yo boy comes in with rash on legs bilaterally after exploring through woods with his friends two days ago. States that the rash is itchy. What type of hypersensitivity?
Type IV
-delayed!
What is rheumatoid arthritis?
Systemic inflammatory tissue where granulationtissue develops in synovialjoint spaces and erodes into articular cartilage and bone
Who is more at risk for RA?
Females>Males
-also has genetic component
RA Presentation
Joint swelling, warmth, erythema, and decreased ROM
Stiffness in morning for >1hr
PIP, MCP, wrist, knees and ankles most affected
Pt comes in with pain in DIP, carpometacarpal joint, and you notice herbdens nodes. Morning stiffness lasts less than one hour and gets worse with effort. What is diagnosis?
Osteoarthritis
-NOT RA
RA has morning stiffness greater than 1hr, worse after rest, and swellings at MCP and PIP with no herbdens nodes
Juvenile Idiopathic Arthritis
Collagen vascular disorder w persistent inflammation in 1 or more joints for 6+ weeks in pt <16 yo
Onset is typically at 1-3yo
-females>males
Presentation of JIA?
Pauciarticular
-Large joints that are asymmetric
Polyarticular
-large and small joints are symmetric
Systemic
- recurrent, high fevers
- myalgia, pericarditis
- anemia, leukocytosis
Systemic Lupus Erythematosus
Inflammatory disorder with recurrent exacerbation and remission, secondary to autoAb formation
-type III hypersensitivity
Who is at most risk for systemic lupus erythematosus?
Females, especially if African American
Also has genetic component of HLA-DR2/DR3
Key characteristics for deciding between SLE and RA
- Morning stiffness lasts minutes for SLE, but hours for RA
- Erosions are uncommon in SLE, but common in RA
- Deforming arthritis uncommon in SLE, but common in RA
What is psoriasis?
Chronic, hyperproliferative inflammatory disorder characterized by thick, adherent scales
Females=males
What is buzzword for psoriasis?
“Salmon pink” plaques with silver white scale
Multiple sclerosis
Demyelination disorder of CNS
Who is at risk for MS?
Females>Males
-genetic component as well
