Viral Infections, Mycosis, Parasitosis Flashcards
What is HPV?
One of the most prevalent viruses in dermatology is HPV. Warts are also an expression of the infection of HPV on the skin. Regarding the morphological appearance of warts on the skin, the primary lesions are papules. A papule is a solid lesion characterized by the presence of the infiltration of something. In the case of warts, the surface is peculiar: you have a papule or plaque if it is larger or a nodule if it is raised on the skin. Considering herpetic lesions, they are characterized by vesicles (liquid full lesions of max 5 mm) which rupture can cause small erosions and the appearance of crusts. Herpetic vesicles are not pyogenic per se. These vesicles are grouped in a grape-like fashion → typical of herpetic appearance.
Etiology of herpes viruses?
They are DNA viruses with high molecular weight which are transmitted by direct cutaneous or mucosal contact. The virus isn’t able to live outside the host, so they transmit directly. There are many types of herpes virus, for dermatological interest mainly HSV1 and HSV2 but there are more like CMV, EBV.
A peculiar characteristic of these infections is latency.
What is the main different between herpes simplex and herpes zoster?
You may experience in your life many recurrences of HSV in oral or in the genital area but you won’t experience shingles (herpes zoster) more than twice throughout your life, so you don’t have many recurrences. Differences are thus in both appearance and pathogenesis.
Primary infection for HSV is asymptomatic or cause sores around the mouth or genitalia while HZ is chickenpox typically in childhood.
Symptoms and affected areas : HSV causes blisters and sores while HZ is more of a painful rash with blisters usually following a single line AKA dermatome where a specific area of the skin is supplied by a single spinal nerve.
Latency and recurrence: in HSV it remains dormant in nerve cells and can reactivate while ZV can also reactivate and express as shingles, but typically only once in a lifetime.
How do we distinguish HSV1 and HSV2?
Usually, we distinguish HSV1 and HSV2 based on their location:
HSV1 is usually located in the upper part responsible for oral manifestations of herpes simplex infection.
HSV2 is usually located in the genitalia.
Phases of infection with virus?
First contact there can be a clinical appearance or not. Incubation is between 2 and 12 days. If it because a clinic it can present fever, inflammation of local lymph nodes and so on.
After the first infection, there is a latency phase where the virus reaches and stays in the sensitive ganglia but when in the host there is immune suppression, cancer, fever or period in the case of a female host, you may have viral reactivation → recurrent phase.
HSV vesicle appearance? In infants?
they are grouped like grapes. Their appearance is so typical that this pattern is called herpetiform lesion. The surrounding skin underneath or close to vesicles is inflamed (erythema or edema). The skin is not a barrier anymore, so it is more prone to be subjected to other infections like bacterial ones (the skin is already not sterile due to bacterial colonization).
In infants it can also be associated to gingivitis and stomatitis.
HSV2?
Most commonly found on genitalia. It is accompanied by local lymph node inflammation, fever and other general symptoms. Risk factors include many sex partners, UV exposure( very uncommon ).
Treatment for viral infections?
Most people use topical antivirals on the vesicles, but this si useless as the virus has already finished its replication. Oral antivirals are the key. Antibiotic cream may be used on the vesicles to avoid concomitant bacterial infections.
How do we diagnoses herpes?
Screening for antibodies, swab and PCR, microscopy and culture.
Herpes zoster clinical appearance?
The first appearance is chicken pox, vesicles all over the body aka varicella.
The second appearance, shingles, may have different locations on the body. Most common dermatomes is the trunk involving 50% of the cases. Others include upper limbs, face, neck and abdomen.
