Derm Rashes, Pruritius, Infections Flashcards
List 4 causes of Itchy skin
- Primary rashes, e.g. eczema or psoriasis
- Infections/ Infestations ( lice/ scabies)
- Metabolic disorders ( uraemia, hyperbilirubinemia)
- Medication related
- Psycho/ social
- Unknown cause
List 3 most common causes of Rashes in the Elderly
20% dermatosis
30% have metabolic causes
50% are idiopathic
Most common type of primary rash?
List 3 others in order of how common each is
Eczema = most common; atopic, irritant, gravitational, asteatotic or discoid
Psoriasis, urticaria, fungal infections, scabies
List 2 rare causes of rashes
- Bullous pemphigoid, pemphigus
- Dermatitis herpetiformis; related to a gluten sensitivity
- Lichen planus
- Cutaneous lymphoma
List some key questions you should ask when taking a history of a rash
List some other rahses which are itchy
- Psoriasis
- Scabies
- Pityriasis Rosea and Versicolor
- Drug rashes; ask when did they start the medication?
- Urticaria
What is Pityriasis Rosea?
What is it a impt ddx for?
Viral infection by Parvovirus B19 which causes a widespread rash which normally starts on the upper torso → can move onto the legs and arms
Differential for guttate psoriasis
Not contagious, usually seen in younger patients
Describe the rash and its progression seen in Pityriasis Rosea?
Rash is ALWAYS proceeded by a Herald Patch → then proceeds to the rest of the eruption
Appears as small tear-shaped, ovoid erythematous, raised, rough feeling eruptions, can be very itchy and widespread
What advice should we give patients with Pityriasis Rosea?
Patients are understandably distressed, therefore always REASSURE them that it is a self-limiting condition and that there is not much that can be done
Normally last about 6-8 weeks
Management of Pityriasis Rosea
Supportive treatments: emollients+ topical steroids if itchy + anti-histamines if persistently itchy
What is Pityriasis vesicolour?
Rash caused by Malassezia furfur (yeast) type infection
Causes a discoloration of the skin+ hypo or hyperpigmentation of the skin
Asymptomatic
Describe the rash seen in Pityriasis vesicolour
Appears as: tan and pale coloured well circumscribed patches/ macules
Bran like surface, fine scale, fairly symmetrical (one of the few infective causes of a rash which IS symmetrical)
Can cause itchiness
Pityriasis vesicolour is often misdiagnosed as Vitiligo, list 3 differences between these
- Hypopigmentation in Versicolor is LESS WELL-DEFINED than Vitiligo
- Vitiligo has more well-defined borders
- Pityriasis = fungal treatment, Vitiligo = steroid treatment
List 4 common cause of drug rashes
- Asprin → flushes, itchiness, rashes
- NSAIDs
- Penicillans
- Allopurinol
Will stopping the drug cause a drug rash to rapidly fade?
No the rash may persist for several days to weeks after you discontinue the medication, then it fades.
Usually, the rash disappears from the top of the body first and the legs and feet last.
How soon within starting the drug does a penicillin rash come on?
Signs and symptoms of penicillin allergy often occur within an hour after taking the drug.
Less commonly, reactions can occur hours, days or weeks later.
List 4 drugs unlikley to cause skin rashes
What is Morbilliform Drug Eruption?
Type of allergic rxn triggered by drug eg. delayed reaction with penicillins
Most common form of drug eruption
Can see a widespread centrally confined, symmetrical, maculo-papular eruption
What is the average interval between taking a new drug and onset of a rash?
Unless the patient has been previously sensitised to a drug, interval between initiation of the therapy and the onset of reaction is rarely < 1wk or > 1month
When during the course is a penicillan rash most likley to appear?
The first time it comes on, it is usually at END of the course or the week afterwards and gets worse
90% of patients who report a penicillin allergy are not allergic
A penicillan rash may often mimic what?
A strep infection or a viral illness - will fade quickly
A patient presents to you requiring Abx, they tell you their mother and sister both had penicillan allergies. Can you prescribe them a penicillan?
Yes, It is not a reason to withhold penicillin if someone in the family is allergic to penicillin
Describe the appearance of a penicillan rash
flat, red patches on the skin accompanied by smaller, paler patches → “maculopapular rash.”
What is Lichen Planus?
Rash that can affect different parts of your body, including inside your mouth
Cause unknown; sometimes related to medications (drug-related licheniform eruptions)
Describe the rash seen in Lichen Planus
Rash eruption with multiple, monomorphic, violaceous type lesions
May have white scaliness on top → Wickham’ striae
Describe the progression Lichen Planus
- Usually starts on distil limbs (wrists and ankles) → Intensely itchy and very painful
- Progresses to multiple lesions all over the body in the widespread form
Can ERUPT anywhere where there has been trauma (or can be spread by scratching)
Treatment of inflammatory disease (eczema, psoriasis, lichen planus, infections etc.)
Topical therapies with sedative antihistamines for short periods only
Topical corticosteroids and topical immunomodulators reduce inflammation, relieve itch and can be applied to broken skin
List an example of a sedating and non-sedating anti-histamines
Sedating: Promethazine
Non-sedating: Loratadine
List 4 types of emolliants and locations where each is used/preffered
- Lotions: scalp, other hairy areas, mild dryness on face, trunk and limbs
- Creams: used when more emollience is required on these later areas
- Ointments: drier, thicker, more scaly areas
- Bath oil
List 4 pieces of advice you can give to a patient about their itch
- Correct low humidity
- Avoid synthetic fabrics
- Pare nails
- Avoid excessive bathing and hot baths
- Moiturisers (dermacol, contains 1% methanol)
- Soap substitute
What is Urticaria and how does it present?
Urticaria = Hives
Rxn which causes raised, red weals of a dermal oedema which are well-defined, can be itchy
Each weal may last a few minutes or several hours and may change shape
Compare acute vs chronic Urticaria
Acute:
- present for less than 6 weeks
- usually self-limiting
- commonly resolves within 24 hours but may last up to 6 weeks
Chronic:
- present for more than 6 weeks
- autoimmunity is the most likely cause
- do routine bloods to check for immunosupression
Neither has long term health consequences other than anxiety and depression.
Is Urticaria an allergy?
Most cases of urticaria are NOT due to allergy → Patch test will NOT help
As it presents as an allergy type reaction, patients are often worried about anaphylaxis. Reassurance is key
List 4 triggers for Urticaria
- Recent illness
- Contact with certain plants, animals, chemicals and latex
- cold – ie. cold water or wind
- rxn to medicine, insect bite or sting
Often the urticaria is triggered by a viral illness or other life event and no obvious cause is found
Investigations for Urticaria
Acute urticaria: Patient’s history and physical examination should direct any diagnostic studies
Chronic/recurrent urticaria: worth doing the following below… But all are likely to be normal
- FBC, CRP, ESR
- TSH/ T4
- Thyroid antibodies
- Anti TTG (gluten) antibodies
- ANA
What is the RAST Test
Radioallergosorbent test → tests for specific IgE antibodies to identify possible allergies
Difficult to interpret and may not be relevant to the current problem i.e. a raised level grass pollen will be related to a patient’s hayfever not their urticaria
Low levels of positives are common AND are usually not relevant.
List 2 other Physical Urticaria
- Cholinergic Urticaria; happens when stressed
- Solar urticaria; from sun exposure
- Cold urticaria
- Pressure urticaria; immediate or delayed; similar to Demographism
- Contact Urticaria
How do we treat Urticaria
Step 1: non-sedating antihistamine daily + menthol
Step 2: If no improvement after 2 wks, ↑ dose of antihistamine (4x standard is safe and effective)
Step 3: if still a problem, can try Monteleukast (LRA; mast cell stabiliser) or adding an H2 antihistamine e.g Ranitidine (less evidene for this)
Are steroids used in Urticaria?
Oral steroids are overused in urticaria
A short course (5-7 days) can be helpful in severe ACUTE urticaria
BUT there is evidence that oral steroids can prolong the course of chronic urticaria; getting rebound on stopping them.
List 4 pieces of general advice about Urticaria
- Reassurance that it is usually self-limitingand is not life-threatening
- Avoid NSAIDs; Aspirin will make it worse
- Avoid Alcohol; getting overtired and try to reduce stress
- Wear loose fitting clothes (put less pressure on the skin)
- Psychological stress can trigger or increase itching
- Avoid known triggers e.g. spicy food
What is Demographia?
A hypersensitivity reaction to trauma - exaggerated response to the firm stroking of the skin
Affects 5% of the population, tends to present in young adults and can occur on its own or with spontaneous urticaria
Symptoms are often worse when the patient is hot and can be triggered by minor pressure e.g. tight areas of clothing
How is demographia treated?
Treatment as per spontaneous urticaria
What is angiodema?
Swelling underneath the skin, usually a reaction to a trigger ie. medicine or allergy
Deeper swelling to simple Urticaria
Pathophysiology and features of angioedema
Incl 2 common locations
Vasodilation and exudation of plasma into deeper tissues
Swelling is generally non-pitting, nonpruritic and occurs on the mucosal surfaces of the respiratory tract and GI tract
Seen on peri-orbital areas and in lips
Is angioedema usually dangerous?
Rarely can be life threatening - Mostly mild and settle spontaneously
What must we ask in a patient with angioedema and WHY?
Ask patient if they have had a voice change
Hoarseness is earliest sign of laryngeal oedema which be life threatening, can also get stridor and respiratory difficulties (rare)
Treatment for severe reactions causing angioedema
Epipen and oral steroids
