Pathology Part 1 Flashcards
Ecchymosis
Large confluent area of purpura (‘bruise’)
Impetigo
Superficial bacterial skin infection usually caused by either S.aureus or Group A Strep.
Can be a primary infection or a complication of an existing skin condition such as eczema, scabies or insect bites.
Causes of Impetigo
o Staph aureus
o Group A strep
Treatment for Impetigo (Limited, localised disease)
- Hydrogen peroxide 1% cream for ‘people who are not systemically unwell or at a high risk of complications’
- Topical antibiotic creams such as topical fusidic acid
Topical mupirocin should be used if fusidic acid resistance is suspected
Treatment for Impetigo (Extensive disease)
Oral flucloxacillin
Oral erythromycin if penicillin-allergic
School exclusion guidelines in Impetigo
Children should be excluded from school until the lesions are crusted and healed or 48 hours after commencing antibiotic treatment
Impetigo features
‘golden’, crusted skin lesions found around the mouth
very contagious
Spread by direct contact
Staphylococcal scalded skin syndrome (SSSS)
A disorder that develops because of a toxin produced by a staphylococcal infection. In SSSS the toxin spreads to the skin through the blood stream and specifically binds to a target protein very high in the epidermis (outer layer of the skin) producing total body reddening of the skin and blistering and sloughing of the skin resembling a hot water burn or scalding of the skin.
Staphylococcal scalded skin syndrome (SSSS) features
- Infancy and early childhood
- Worse over face, neck, axillae and groin
- Scald-like skin appearance followed by large flaccid bulla
Cause of Staphylococcal scalded skin syndrome (SSSS)
Bullous impetigo
Treatment for Staphylococcal scalded skin syndrome (SSSS)
Flucloxacillin
Difference between Staphylococcal scalded skin syndrome and Toxic epidermal necrolysis (TEN)
Differentiated by
• Mucosal involvement only occurs in TEN
• Skin biopsy; more superficial split in SSSS than TEN
Cellulitis
An inflammation of the skin and subcutaneous tissues, typically due to infection by Streptococcus pyogenes or Staphylcoccus aureus.
Features of cellulitis
- commonly occurs on the shins
- erythema, pain, swelling
- systemic upset such as fever
- Often blisters especially is oedema is present
Causes of cellulitis
- Group A strep
- S.aureus
- May be an obvious portal of entry for infection
Eron classification
To guide how we manage patients with celluliti
Categories for admitting patient wit cellulitis for IV antibiotics
- Has Eron Class III or Class IV cellulitis.
- Has severe or rapidly deteriorating cellulitis (for example extensive areas of skin).
- Is very young (under 1 year of age) or frail.
- Is immunocompromized.
- Has significant lymphoedema.
- Has facial cellulitis (unless very mild)
Management of mild/moderate cellulitis
Flucloxacillin as first-line
Clarithromycin, erythromycin (in pregnancy) or doxycyline is recommended in patients allergic to penicillin.
Management of severe cellulitis (based on categories)
IV antibiotics
Necrotising fasciitis
Is a rare but serious bacterial infection that affects the tissue beneath the skin and surrounding muscles and organs (fascia).
Necrotising fasciitis classifications
Type 1 is caused by mixed anaerobes and aerobes (often occurs post-surgery in diabetics). This is the most common type
Type 2 is caused by Streptococcus pyogenes
Necrotising fasciitis risk factors
- Skin factors: recent trauma, burns or skin infections
- Diabetes mellitus
- Intravenous drug use
- Immunosuppression
Features of Necrotising fasciitis
> Widespread tissue destruction > Acute onset > Severe pain > Fever > Necrosis
Fournier’s gangrene
Sometimes life-threatening form of necrotizing fasciitis that affects the genital, perineal, or perianal regions of the body.
Most commonly affected area in Necrotising fasciitis
The most commonly affected site is the perineum (Fournier’s gangrene).
Management of Necrotising fasciitis
Urgent surgical referral debridement
Intravenous antibiotics such as benzylpenicillin and clindamycin
Folliculitis
- Inflammation of the hair follicle
- Caused by staph aureus
- Caused by Pseudomonas ovale with hot tub use
Folliculitis features
- Presents as itchy or tender papules and pustules
- Commoner in humid climates
- Hot tub use
- Extensive, itchy folliculitis of the upper trunk - possibility underlying HIV infection
Management of Folliculitis
Oral erythromycin
Leprosy
A granulomatous disease primarily affecting the peripheral nerves and skin. It is caused by Mycobacterium leprae.
Cause of leprosy
Mycobacterium leprae.
Classifications for Leprosy
- Interdeterminate leprosy
- Tuberculoid leprosy
- Lepromatous leprosy
Interdeterminate leprosy
Small hypopigmented or erythematous circular macules with occasional mild anaesthesia and scaling
May resolve spontaneously or progress to one of the other types
Tuberculoid leprosy
Few larger hypopigmented or erythematous plaques with an active erythematous, often raised, rim.
Lesions are usually marked, dry and hairless (reflecting the nerve damage)
Nerves may be enlarged and palpable
Lepromatous leprosy
Presents with multiple inflammatory papules, plaques and nodule
Loss of the eyebrows and nasal stuffiness are common
Skin thickening and severe disfigurement and may follow
Diagnosis of Leprosy
- Hypopigmented/reddish patches with sensory loss
- Thickening of peripheral nerves
- Acid fast bacilli seen on skin-slit smears/biopsy
Management of leprosy
Triple therapy: rifampicin, dapsone and clofazimine
Leprosy features
> Patches of hypopigmented skin
buttocks, face, and extensor surfaces of limbs
Sensory loss
Slapped cheek syndrome
- Infection Caused by parvovirus B19
- Bright red rash seen on the face (slapped cheek)
- Arthritis
Another name for Slapped cheek syndrome
Erythema infectiosum
Features of HSV infection
May present with a severe gingivostomatitis
Cold sores
Painful genital ulceration
Can autoinoculate into sites of trauma and present as painful blisters/pustules
Herpetic whitlow
HSV strain types
HSV-1 & HSV-2
Herpetic whitlow
A painful infection of the finger caused by the herpes virus. It’s easily treated but can come back - typically seen in healthcare workers
Management for HSV infection
Oral aciclovir for gingivostomatitis and genital herpes
Topical aciclovir for cold sores
Management of pregnant women with HSV primary attack at >28 weeks gestation
C-section at term is advised if a primary attack of herpes occurs during pregnancy at greater than 28 weeks gestation
Complications of HSV infection
- Corneal ulceration
- Eczema herpeticum
- Erythema multiforme
Varicella zoster virus
Produces two distinct diseases:
- Chickenpox (varicella)
- Shingles
Chicken pox
Occurs in childhood
Virus entering through the mucosa of the upper respiratory tract
Air borne transmission
Shingles
> Arises from the reactivation of latent viruses
> Most common in the elderly
Varicella zoster virus infection
Chickenpox = none Shingles = acyclovir
Hutchenson’s sign
Presence of vesicular lesions on the side or tip of the nose - Acute herpes zoster ophthalmicus and shingles
What two conditions are associated with Hutchenson’s sign?
Acute herpes zoster ophthalmicus
Shingles
Features of Shingles
> Unilateral and restricted to a single dermatone
Neuralgic pain
Hutchenson’s sign
How does Varicella zoster virus lead to shingles?
Following recovery of chickenpox in childhood, the virus remains latent in dorsal root and cranial nerve ganglia
Reactivation of infection then results in shingles
Management of pregnant woman with recurrent herpes
Should be treated with suppressive therapy and be advised that the risk of transmission to their baby is low.
What strains of HPV is associated with genital warts?
6 and 11
What strains of HPV is associated with cancer?
Types 16, 18 and 33
What strains of HPV is associated with non-genital warts?
Types 1 to 4
Molluscum Contagiosum
A common skin infection caused by molluscum contagiosum virus (MCV), a member of the Poxviridae family.
Transmission of Molluscum Contagiosum
Transmission occurs directly by close personal contact, or indirectly via fomites (contaminated surfaces) such as shared towels and flannels.
Highly contagious
Features of Molluscum Contagiosum
- Highly contagious
- Small, firm, umbilicated pearlescent nodules
- Look fluid filled but are solid
- Not painful, but itchy
- Common in children, can transmit sexually
Onychomycosis
Is a fungal infection of the nails
Dermatophytes
Are fungi that require keratin for growth. These fungi can cause superficial infections of the skin, hair, and nails.
Causes of onychomycosis
- Dermatophytes - mainly Trichophyton rubrum
- Yeasts - such as Candida
- Non-dermatophyte moulds
Risk factors for onychomycosis
Diabetes mellitus
Increasing age.
Investigations of onychomycosis
Nail clippings
Scrapings of the affected nail
Management of onychomycosis
Asymptomatic = none
Dermatophytes - oral terbinafine/itraconazole
Candida - Amorolfine/itraconazole
Dermatophyte nail infection management
Oral terbinafine first-line with oral itraconazole as an alternative
Fingernails - 6 weeks - 3 months therapy
Toenails - 3 - 6 months therapy
Candida infection management
Mild disease - topical antifungals (e.g. Amorolfine) Severe infections - oral itraconazole for a period of 12 weeks
Tinea cruris
Dermatophyte infection affecting the groin
Tinea pedis
Dermatophyte infection affecting the foot
Tinea manuum
Dermatophyte infection affecting the palms
Tinea unguium
Dermatophyte infection affecting the nails
Tinea capitis
Dermatophyte infection affecting the scalp
Tinea corporis
Dermatophyte infection affecting the whole body
Pityriasis versicolor
Also called tinea versicolor, is a superficial cutaneous fungal infection caused by Malassezia furfur (formerly termed Pityrosporum ovale)
Features of Pityriasis versicolor
> White people - red/brown scaly macules
Black people - hypo pigmented macules
May be more noticeable following a suntan
Scale is common
Mild pruritus
Management of Pityriasis versicolor
Ketoconazole shampoo
If failure to respond to topical treatment then consider alternative diagnoses (e.g. send scrapings to confirm the diagnosis) + oral itraconazole
Scabies
Caused by the mite Sarcoptes scabiei and is spread by prolonged skin contact. It typically affects children and young adults.
Pathophysiology of scabies
The scabies mite burrows into the skin, laying its eggs in the stratum corneum. The intense pruritus associated with scabies is due to a delayed-type IV hypersensitivity reaction to mites/eggs which occurs about 30 days after the initial infection.
Scabies features
> Widespread pruritus
Linear burrows on the side of fingers, interdigital webs and flexor aspects of the wrist
In infants, the face and scalp may also be affected
secondary features are seen due to scratching: excoriation, infection
Management of Scabies
- permethrin 5% is first-line
2. malathion 0.5% is second-line
Crusted (Norwegian) scabies
Seen in patients with suppressed immunity, especially HIV.
Treatment of crusted (Norwegian) scabies
Ivermectin is the treatment of choice and isolation is essential
Guidance on management of scabies patient and close contacts
Avoid close physical contact with others until treatment is complete
All household and close physical contacts should be treated at the same time, even if asymptomatic
Linear or curved skin burrows
Scabies
Common sites of infection for scabies
Between the webs of the fingers and toes
Lice
- Blood sucking parasites
- Can affect the head, body, or pubis
- Presents with itch, excoriations
Atopic eczema
Atopic eczema (atopic dermatitis) is the most common form of eczema, a condition that causes the skin to become itchy, dry and cracked.
Atopic eczema features
- Extensor aspects in infants, flexor aspect in adults
- Chronic itching/rubbing can lead to lichenification
- Often positive family history of atopy
Treatment for Atopic eczema
o Avoid exacerbating agents o Frequent emollients o Topical steroids for flareups o Antivirals if secondary herpes infection o Phototherapy for severe cases
Pathophysiology of eczema
The simplified pathophysiology is that eczema is caused by defects in the barrier that the skin provides.
Tiny gaps in the skin barrier provide an entrance for irritants, microbes and allergens that create an immune response, resulting in inflammation and the associated symptoms.
Steroid potency ladder
Mild: Hydrocortisone 0.5%, 1% and 2.5%
Moderate: Eumovate (clobetasone butyrate 0.05%)
Potent: Betnovate (betamethasone 0.1%)
Very potent: Dermovate (clobetasol propionate 0.05%)
Discoid eczema
A morphological variant of eczema characterised by well-demarcated scaly patches, especially on the limbs
Tends to follow an acute/sub-acute rather thana chronic pattern - Often an infective component
Eczema herpeticum
A viral skin infection in patients with atopic eczema caused by the herpes simplex virus 1 or 2.
Management of Eczema herpeticum
Emergency - IV aciclovir
Sebhorrhoeic eczema
- Affects body sites rich in sebaceous glands
- Neonates – yellow thick crusts on scalp
- No pruritus
Varicose eczema
- Tends to occur in older people, especially women
- Usually lower legs and ankles
- Past history of venous thrombosis
- Leg ulcer or varicose veins may be present
Varicose eczema management
- Compression stockings
- Emollients
- Moderately potent topical steroids
Asteatotic eczema
Also known as winter eczema, eczema craquele, senile eczema - Often occur in elderly people
Dry plate-like cracking of the skin with a red, eczematous component - “Crazy paving pattern”
Causes of allergic contact dermatitis
> Nickel > Chromate > Latex > Perfume > Hair dye
Causes of irritant contact eczema
>
Detergents Soaps Bleach
Treatment for irritant and allergic contact eczema
- Avoid the causative agent
- Wear protective gloves
- Change occupation/hobbies
Irritant contact dermatitis
Common - non-allergic reaction due to weak acids or alkalies (e.g. detergents). Often seen on the hands. Erythema is typical, crusting and vesicles are rare
Allergic contact dermatitis:
Type IV hypersensitivity reaction. Uncommon - often seen on the head following hair dyes. Presents as an acute weeping eczema which predominately affects the margins of the hairline rather than the hairy scalp itself.
Two types of contact eczema/dermatitis
- Irritant
2. Allergic
Lichen simplex
A localised area of chronic, lichenified eczema/dermatitis. There may be a single or multiple plaques. It is also called neurodermatitis.
Common sites for Lichen simplex
> Nape of the neck > Lateral calves > Upper thighs > Upper back > Scrotum > Vulva
Cow’s milk protein intolerance/allergy features
- regurgitation and vomiting
- diarrhoea
- urticaria, atopic eczema
- ‘colic’ symptoms: irritability, crying
- wheeze, chronic cough
- rarely angioedema and anaphylaxis may occur
Management of Cow’s milk protein intolerance/allergy if formula-fed
Extensive hydrolysed formula (eHF) milk is the first-line replacement formula for infants with mild-moderate symptoms
Management of Cow’s milk protein intolerance/allergy if breast-fed
Continue breastfeeding
Eliminate cow’s milk protein from maternal diet.
