Skin infections and infestations Flashcards
How do HSV-1 and HSV-2 infections differ in manifestation?
HSV-1 is traditionally associated with orofacial infection, while HSV-2 is traditionally associated with genital infection, although there is considerable overlap in disease manifestations.
In what % of cases is primary infection of HSV asymptomatic?
80% of cases
Describe latency in HSV infections of both orofacial infections and genital infections
Latency is the establishment and maintenance of latent infection in nerve cell ganglia proximal to the site of infection:
o In orofacial infection the trigeminal ganglia are most commonly involved
o In genital infection the sacral nerve root ganglia (S2-S5) are involved
How do primary and secondary HSV infections differ?
Primary HSV infections are accompanied by systemic signs, longer duration of symptoms, and higher rate of complications. Recurrent episodes are milder and shorter
What is the most common presentation of HSV-1 infections?
Herpetic gingivostomatitis
When do most cases of herpetic gingivostomatitis occur?
Most cases arise between the ages of six months to five years
What are the clinical features of herpetic gingivostomatitis?
Clinical features include:
- systemic upset
- lymphadenopathy
- gingivitis
- painful, white vesicles on tongue, buccal mucosa, palate, pharynx and lips
How long do the symptoms of herpetic gingivostomatitis persist?
The main symptoms persist for 5-7 days, and are fully resolved within two weeks
What is the proper name for cold sores?
Herpes labialis
What does recurrent infections of orofacial herpes simplex infections usually present as?
Herpes labialis (syn. cold sore)
What triggers Herpes labialis (syn. cold sore)?
Triggers are many, including UV-radiation, minor trauma and stress
Describe the clinical presentation of Herpes labialis
The clinical presentation of a cold sore is that of grouped vesicles, especially of the lips and perioral skin. The eruption is often preceded by a tingling, itching or burning sensation. Over a few days the vesicles form a crust, and the eruption resolves within 7-10 days
What can cause herpes genitalis?
Can be caused by both HSV-1 and HSV-2, and is usually sexually transmitted
Which HSV virus is more commonly associated with recurrent herpes genitalis?
HSV-2
How can herpes genitalis present in both men and women?
Systemic symptoms may precede the development of painful ulcers in both men and women
In women, ulcers can affect the external genitalia, as well as the vagina and cervix, which is involved in 70%-90% of cases. Dysuria may be severe and can cause urinary retention
In men, ulcers are most commonly seen on the glans, prepuce and shaft of the penis. Occasionally they can extend on to the scrotum, thighs, and buttocks. Approximately one-third of men will develop a urethritis
The perianal area and rectum may be involved with anal intercourse
What % of cases in women with herpes genitalis have their vaginas and cervixes affected?
70-90% of cases
Describe Inoculation herpes simplex
HSV can enter through an abrasion (e.g. shaving), to affect any part of the skin e.g. face, vulva etc
Lesions arise as vesicles, and sometimes bullae, either grouped as a plaque or scattered. Systemic upset tends to be minimal
Some well-described sites include the fingertips (a herpetic whitlow), where episodes can be recurrent, and on the face of rugby players, which is referred to as ‘scrumpox’
What are some more unusual presentations of HSV infections?
- Keratoconjunctivitis
- Eczema herpeticum
- Neonatal herpes simplex
- Disseminated herpes simplex
- Erythema multiforme
Describe keratoconjunctivitis
As with herpes zoster, a primary herpes simplex infection can lead to severe inflammation with the potential for damage to the cornea and conjunctivitis and blindness in the affected eye
Describe Eczema herpeticum
Atopic patients are at risk of developing extensive eruptions of herpes simplex known as eczema herpeticum
The condition presents with clusters of itchy or painful vesicles / punched-out monomorphic erosions, which may coalesce
Any site can be affected, most commonly the face and neck. Lesions can occur in normal skin or in sites actively or previously affected by atopic eczema or other skin conditions
New patches form and spread over a period of 7 to 10 days, and can become widespread
Describe neonatal herpes simplex
Genital herpes simplex at the time of delivery makes the risk of neonatal infection very high
Infection can also arise in the neonatal period
Symptoms vary from a localised cutaneous infection to disseminated herpes simplex
Describe disseminated herpes simplex
Those at risk are immunocompromised patients (e.g. those on chemotherapy), and neonates not protected by maternally acquired antibodies. It rarely occurs in healthy individuals
Cutaneous lesions may be clinically indistinguishable from those of herpes zoster
Systemic infection, such as hepatitis and encephalitis may develop with or without widespread cutaneous lesions.
Why is it important to distinguish early on between disseminated herpes simplex and disseminated herpes zoster?
The mortality from disseminated HSV is higher than that from disseminated zoster, so early recognition and treatment is essential
Describe Erythema multiforme (EM)
- Is characterised by macular, papular or urticated lesions, as well as the classical ‘target lesions’ distributed preferentially on the distal extremities. Mucosal surfaces may be involved
- EM is a hypersensitivity reaction usually triggered by infections, most commonly herpes simplex. The infection may present as a cold sore, or may be subclinical
How is primary herpetic gingivostomatitis and herpes genitalis treated?
Consider treatment with oral aciclovir 200 mg five times daily for 5 days. Adjust the dose accordingly in children
Alternatively use valaciclovir or famciclovir
Treatment will shorten the duration of an attack but does not prevent future attacks
In addition, for herpes genitalis, patients and their partners need screening for other sexually transmitted disease
How is recurrent herpes labialis treated?
Reduce risk factors eg advise on appropriate UV-protection
5% aciclovir cream can be helpful if used as soon as patients are aware that a recurrence is occuring
For very frequent / distressing attacks consider prophylactic aciclovir 200-400 mg BD (alternatively use valaciclovir or famciclovir)
How is recurrent herpes genitalis treated?
Treat with prophylactic aciclovir 400 mg BD (alternatively use valaciclovir or famciclovir)
How is recurrent herpes simplex associated with recurrent erythema multiforme treated?
Treat with prophylactic aciclovir 400 mg BD (alternatively use valaciclovir or famciclovir), adjust the dose accordingly in children
What is important to educate a HSV patient on for long term control and treatment?
It is important to recognise potentially life-threatening systemic infections, which are much more likely in immunocompromised patients and neonates
Patients need admitting urgently for treatment with high-dose intravenous antiviral therapy
Who is most commonly affected by herpes zoster?
Herpes zoster is more common in adults, especially the elderly, the unwell, and the immunosuppressed
Not uncommon in kids, but generally quite mild
What is usually the first manifestation of herpes zoster?
Pain, which may be severe, and may be accompanied by fever, headache and malaise
How long is there between the start of pain and the onset of skin eruption in both trigeminal and thoracic herpes zoster?
The time between the start of the pain and the onset of the skin eruption averages 1.4 days in trigeminal zoster and 3.2 days in thoracic disease
Describe the clinical features of herpes zoster infections
Dermatomal distribution of closely grouped red papules, rapidly becoming vesicular and then pustular, develop in a continuous or interrupted band in the area of one or occasionally two and, rarely, more contiguous dermatomes
New vesicles continue to appear for several days
In some patients lesions become much larger and necrotic
What dermatomes are affected by herpes zoster?
o Thoracic 53%
o Cervical 20%
o Trigeminal, including ophthalmic 15%
o Lumbosacral 11%
Describe herpes zoster oticus and the Ramsay-Hunt syndrome
Peripheral facial nerve palsy accompanied by an erythematous vesicular rash on the ear (herpes zoster oticus) or in the mouth
Is caused by varicella zoster virus (VZV) infection of the head and neck involving the facial nerve (seventh cranial nerve).
Describe herpes zoster ophthalmicus
Skin lesions are located in the dermatome of the nasociliary nerve. This area includes not only the tip of the nose, but also involves the skin at the inner corner of the eye, and the root and side of the nose (Hutchinson’s sign)
Contact ophthalmologist ASAP to ensure sight isn’t affected
Describe disseminated herpes zoster and who is mainly affected
The risk of cutaneous dissemination, which has been defined as more than 20 vesicles outside the area of the primary and adjacent dermatomes, increases with age
Life-threatening systemic dissemination is rare, and mainly affects patients with lymphoma and other immunocompromised conditions
What is Hutchinsons sign?
Vesicles on the tip of the nose, or vesicles on the side of the nose, precedes the development of ophthalmic herpes zoster. This occurs because the nasociliary branch of the trigeminal nerve innervates both the cornea and the lateral dorsum of the nose as well as the tip of the nose
What is postherpetic neuralgia?
o Is defined as the persistence or recurrence of pain more than one month after the onset of herpes zoster
o It becomes increasingly common with age, affecting about one-third of patients aged over 40. It is particularly likely if there is facial involvement
o The pain may be continuous and burning with increased sensitivity in the affected areas or a spasmodic shooting type of pain. Some patients complain of an itch and a crawling sensation. The overlying skin can be numb or exquisitely sensitive to touch
What is standard treatment of herpes zoster virus?
Adults - oral antiviral therapy e.g. aciclovir tablets, 800 mg five times a day for seven days
Children - in healthy children the condition is often relatively mild and may not require treatment, however, children who take courses of systemic steroids, e.g. for asthma, are rendered vulnerable for up to three months after treatment is complete - if the child develops chickenpox in this period parents should seek urgent competent advice as treatment with oral antiviral therapy will be required
Who should be closely monitored while on herpes zoster treatment?
Children who take courses of systemic steroids, e.g. for asthma, are rendered vulnerable for up to three months after treatment is complete - if the child develops chickenpox in this period parents should seek urgent competent advice as treatment with oral antiviral therapy will be required
How is herpes zoster treated in immunocompromised patients?
Should continue on with oral antiviral therapy for two days after crusting of the lesions
If the patient is unwell / develops widespread (disseminated) zoster, admission will be needed
How is ophthalmic zoster treated?
All patients with ophthalmic zoster, irrespective of age or severity of symptoms, should be prescribed oral antiviral drugs at the first sign of disease
Patients with a red eye or visual complaints must be referred to an ophthalmologist on an urgent basis
Those not needing referral must be reviewed after at most one week
How is herpes zoster with Ramsay Hunt syndrome treated?
Oral antiviral therapy must be started immediately and contact the on-call ENT team
Some advocate the use of systemic steroids - refer to local guidelines for management
How is postherpatic neuralgia treated?
Tricyclic antidepressants such as amitriptyline, or anticonvulsants such as gabapentin, are the mainstay of treatment
What is impetigo?
Impetigo is a highly contagious bacterial skin infection causing blisters and sores. Impetigo mainly affects children, often on the face, especially around the nose and mouth, and sometimes on the arms or legs. The two types of impetigo are bullous impetigo and non-bullous impetigo
Describe the pathogens that cause both non-bullous and bullous impetigo
Impetigo - in the UK Staphylococcus aureus is the most common organism, Streptococcus pyogenes is the other pathogen involved, and on occasions both organisms can be found together. In warmer climates Streptococcus pyogenes is more prevalent
Bullous impetigo - is nearly always caused by Staphylococcus aureus
Methicillin-resistant Staphylococcus aureus (MRSA) is an increasingly common cause of impetigo, and is associated more often with the non-bullous form
Who is most commonly affected by both non-bullous and bollous impetigo?
Although impetigo can affect any age, the non-bullous form is most common in children 2-5 years of age, and bullous impetigo under the age of 2 years
What investigations are carried out for impetigo?
- Impetigo is usually diagnosed on the basis of the clinical appearance
- Poorly responsive or recurrent cases of impetigo should be swabbed for C&S to identify possible methicillin-resistant Staphylococcus aureus (MRSA). Swabs are best taken from a moist lesion, or, in cases of bullous impetigo from a de-roofed blister
What general measures are taken to treat impetigo?
o Provide a patient information leaflet on impetigo
o Cover affected areas where possible
o Wash hands regularly
o Use separate towels and flannels
o Avoid school until the lesions are healed or crusted over, or 48 hours after antibiotics are started
How is local/mild impetigo treated?
o First-line treatment is topical fusidic acid for 7-10 days
o In cases of fusidic acid resistance, use topical mupirocin
How is widespread impetigo treated?
Use a systemic antibiotic for 7 days, either flucloxacillin or erythromycin / clarithromycin. Reasons for choosing the latter include cases of penicillin allergy, or if there are concerns with regards to compliance with flucloxacillin given its unpleasant taste and QDS dosing regime
How is persistent or recurrent impetigo treated?
The nose is one of the most common sites of carriage for Staphylococcus aureus, so treatment of recurrent cases should include the application of nasal mupirocin up both nostrils BD for 5 days
Wash the whole body daily with antibacterial emollient, eg the Dermol range, or anti-septic, eg chlorhexidine
Consider a prolonged course of oral antibiotics for up to six weeks
Identify and treat other carriers and possible sources of re-infection - it may be useful to take nasal swabs from other household contacts even if they do not have any cutaneous symptoms
If strep. causes impetigo, what could be a possible complication?
Streptococcal infection occasionally causes acute glomerulonephritis
What is folliculitis and what is the common causative agent?
Folliculitis is a common skin condition in which hair follicles become inflamed. It’s usually caused by a bacterial or fungal infection. At first it may look like small red bumps or white-headed pimples around hair follicles.
Commonly associated with Staph infections
What is a carbuncle and what is the common causative agent?
A carbuncle is a red, swollen, and painful cluster of boils that are connected to each other under the skin. A boil (or furuncle) is an infection of a hair follicle that has a small collection of pus (called an abscess) under the skin
Commonly caused by Staph infections
Describe Erysipelas
Erysipelas is an acute infection typically with a skin rash, usually on any of the legs and toes, face, arms, and fingers. It is an infection of the upper dermis and superficial lymphatics, usually caused by beta-hemolytic group A Streptococcus bacteria on scratches or otherwise infected areas
Erysipelas is more superficial than cellulitis, and is typically more raised and demarcated
Wha is the most common cause of erysipelas
Usually caused by beta-hemolytic group A Streptococcus bacteria on scratches or otherwise infected areas
Describe cellulitis
Cellulitis is a bacterial infection involving the inner layers of the skin. It specifically affects the dermis and subcutaneous fat. Signs and symptoms include an area of redness which increases in size over a few days. The borders of the area of redness are generally not sharp and the skin may be swollen. While the redness often turns white when pressure is applied, this is not always the case. The area of infection is usually painful. Lymphatic vessels may occasionally be involved, and the person may have a fever and feel tired.
What is the causative agent of scabies?
Human scabies is caused by infection with a mite known as Sarcoptes scabiei var. hominis.
Describe scabies
Itch, which is characteristically worse at night
Scabies should be part of the differential diagnosis of any itchy rash where no other cause can be readily identified. It is possible for patients with eczema to also acquire scabies
Where is mostly affected on the body by scabies?
The trunk and limbs are the predominant sites that are affected
The face and scalp are rarely involved other than in infants and bed-bound elderly patients
Describe the morphology of scabies
A generalised rash with erythema, papular and urticated lesions. This is caused by an allergy to the mites and their products, and may take several weeks to develop after infestation
Burrows - are seen as very small irregular tracks. These are most common on the sides of fingers, the webs, the borders of the hands, the wrists and the feet. They can also be found on the male genitalia, axillae and buttocks
Papules and nodules - most commonly seen on the shaft of the penis (pathognomonic), the groins and in the axillae. They may persist for several weeks after the scabies has been eradicated
Papules and pustules on the palms and soles are characteristic of scabies in infancy
What is crusted scabies?
Crusted scabies (syn. Norwegian scabies) is an uncommon form of scabies which is highly contagious.
It most commonly arises in patients with the following:
• Dementia
• Down’s syndrome
• Conditions associated with neurological impairment
• Immunosuppression
• Those who have been inappropriately treated with potent or super-potent topical steroids
Clinical features - generalised scaly rash. The itch is often significantly less than with classical scabies. The scalp may be involved
In which groups is crusted scabies most commonly seen in?
It most commonly arises in patients with the following:
• Dementia
• Down’s syndrome
• Conditions associated with neurological impairment
• Immunosuppression
• Those who have been inappropriately treated with potent or super-potent topical steroids
How is scabies treated?
5% permethrin cream (Lyclear ®) is the treatment of choice and is safe to use in pregnancy; other scabicides are more irritant and less effective. 1 x 30 g tube should cover an average adult
The cream should be applied uniformly over all the body from the neck downwards. Every inch of skin must be covered with special attention paid to skin creases, the genitalia and underneath the nails. The face and scalp should only be treated if they are affected, which is uncommon in adults and older children - Lyclear ® cream rinse should be used for the scalp
Wash off after 8 to 24 hours (note the cream should be re-applied to the hands if they are washed within 8 hours of first applying the cream)
Repeat treatment after seven days
Treat secondary infection if present with a systemic antibiotic e.g. flucloxacillin, or erythromycin if the patient is allergic to penicillin
How are patient contacts of those who have scabies treated?
This includes anyone living in the same house, partners and others who have significant contact though child care eg in some situations grandparents
Remember other contacts can be infected with scabies but remain asymptomatic for several weeks
All such contacts need to be managed in exactly the same way as the patient, however for most only one treatment is needed. Only symptomatic contacts require two treatments
How should persistent symptoms of scabies be treated?
The itch of scabies may not clear for at least a month after successful eradication of the mite. Treatment with Eurax HC ® cream helps reduce itch and it also acts as a mild scabicide.
Nodules, which are not contagious, can occasionally persist for several months and should be treated with a moderately potent topical steroid
How is severe or crusted scabies treated?
Patients need frequent applications of permethrin, sometimes for several weeks. Oral ivermectin is sometimes used in such cases
When should a discussion/referral to a dermatologist be considered in scabies cases?
o Diagnostic uncertainty / failure to respond to adequate treatment of the patient and contacts
o Crusted scabies
o An outbreak in a nursing or other care home
