Hypersensitivity Reactions & Paed Derm Flashcards
This type of hypersensitivity reaction involves prior sensitisation of mast cells with antigen-specific IgE antibodies. These mast cells then degranulate on further contact with the antigen causing mass production of histhamine, heparin and tryptase.
Type 1 - causing urticaria, angiodema, anaphylaxis Anything from pollen to nuts…
This type of hypersensitivity reaction is auto-immune, IgG or IgM antibodies bind to bodie’s cells, neutrophils are stimulated to attack the cells, causing inflammatory damage. (4 egs. 2 thyroid, 1 NMJ, 1 skin)
Type 2 - Hashimoto’s disease (thyroid), Myasthenia gravis (NMJ), Grave’s (thyroid), Pemphigoid / pemphigus
This type of hypersensitivity reaction is due to agglutination of multiple IgM antibodies around an antigen - creating an antibody/antigen complex which is large and get’s stuck in micro vessels - 2 e.g.s of ways in which this can present.
Type 3 - If complex blocks vessels can cause thrombosis & purpura e.g. Vasulitis Lupus Septicaemia if blocks glomerulus - Glomerulonephritis.
This type of hypersensitivity reaction is delayed onset - the antigen is presented by dendritic cells to CD4+ T cells, which stimulate the activation of CD8 T cells, which then travel to the site of irritation and cause inflammatory response (itchy, red, vesicles)
Type 4 - Can take days, e.g. drug reactions, occupational workers e,g, sawdust, poison ivy (USE)
4 common types of skin problems in children / young people
Atopic eczema Infections / fungal infestations Viral exanthemas Acne
What is the atopic triad
asthma, eczema, allergic rhinitis
What is this
Atopic eczema
•Usually appears first <2 years old, typically at 4-6 months old
Face and neck often first sites to erupt
What is this - what is a distinguishing feature in this photo
Eczema - often flexor surfaces such as elbow and knee creases.
If it DOESN’T ITCH THEN IT ISNT ECZEMA
Common secondary infection of eczema?
Staph aureus
List these topical corticosteroids in order of potency from LEAST potent to MOST:
Mometasone furoate (Elocon)
Clobetasone butyrate 0.05% (Eumovate)
Clobetasol propionate 0.05% (Dermovate)
Hydrocortisone acetate 1%
Betamethasone valerate (Betnovate)
Hydrocortisone acetate
Moderately potent Clobetasone butyrate 0.05%
(Eumovate)
Potent Mometasone furoate (Elocon)
Betamethasone valerate (Betnovate)
Very potent Clobetasol propionate 0.05%
(Dermovate)
What is this, what causes it?
Steroids causing skin striae and thinning
Pimecrolimus and Tacrolimus are what type of drug? How to they work and what is the minimum age they should be used for?
Immunomodulating drugs - creams / ointments - reduce T cell activation.
Only for > 2yrs old
No skin thinning side effects
What is the effect on Tacrolimus blood concentrations if you take Rifampicin or Carbamazepine?
Blood conc will decrease, Rifampicin and Carbamazepine are CYP enzyme inducers so increase the metabolism of Tacrolimus.
A 32 yr old with known eczema presents with this rash after having a cold sore for a few days - cause?
Eczema herpeticum - Herpes simplex infection spreads systemically - req. antivirals eg acycolvir orally for 5 days
What is this, what is its relevance in eczema patients?
Molluscum contagiosum - more comon in eczema patients
Viral infection - common in kids, usually resolves within few months.
Small firm raised papules, not painful but can be itchy.
Herpes simplex virus
Is is contagious?
What skin layers does it affect?
Where does the virus remain dormant?
Is this a recurrant infection?
•Highly contagious by direct contact (Primary infection)
•
•Penetrates the epidermis or mucous membrane
•
•Epidermal cell destruction•Virus hides latent in the dorsal root ganglia (Sensory)
•
•Reactivation – Recurrence is the hallmark
What is this
Varicella zoster - Chickenpox
•Incubation - 2 weeks
•Febrile illness•Crops of vesicles
•Infectious till crusts
•
•Can become purulent
•May scar
What is this?
Incubation time?
Signs / symptoms?
Key diagnostic sign in mouth?
Measles
- Prodromal period 10-12 days after exposure
- Fever, conjunctivitis, coryza (runny nose) and cough
- 2-3 days Kopliks spots
- 4-5 days rash – starts on head, rapidly spreads all over
- High fever (>40 degrees C)
What is shown here? What disease is this a sign of?
Koplik spots - Measles
What disease is:
•Usually mild disease, slight fever and sore throat
•Rash - starts on head spreads down
•Tender lymph nodes – occipital, behind ears
Can develop “blueberry muffin” = congenital disease acquired from mother in pregnancy
Rubella (German Measles)
Symptoms of congenital rubella include deafness, eye problems e.g. cataracts,
Heart problems eg PDA
Possibly purple lumps hence the “blueberry muffin” thing?
What is this disease, also known as “fifth disease”?
What is the causative organism and key features?
- Erythema infectiosum due to parvovirus B19
- Mild illness- “slapped cheek” appearance the first sign
- Lacey rash, may be in glove and stocking distribution a few days later
What is this disease, also known as “fifth disease”?
What is the causative organism and key features?
- Erythema infectiosum due to parvovirus B19
- Mild illness- “slapped cheek” appearance the first sign
- Lacey rash, may be in glove and stocking distribution a few days later
Hand foot and mouth disease is most common at what time of year, causing what features, what is the causative organism?
- Enterovirus infection (Coxsackie A)
- Outbreaks in summer
- Small flat blisters on hands and feet, mouth ulcers
This infection is:
•Spread by direct physical contact.
•Takes 4-6 weeks to become sensitised
•Burrows are definitive lesions
Often between fingers and toes
Scabies mite - Sarcoptes scabei
