Managing skin infections and infestations Flashcards
This is a dermatomal rash, which is a strong clue this is Varicella Zoster, aka Herpes zoster infection.
C is incorrect because this patient has involvement of the skin around their eye, implying that the eye itself could be involved in that and the ocular nerve, and that can cause complications such as blindness, and therefore you shouldn’t delay treatment. The role of diagnostic confirmation is important, but it shouldn’t delay treatment particularly since it’s a classic presentation and the treatment isn’t dangerous.
Exfoliative toxins are virulence factors of staphylococcus aureus. Remember that the presentation of staphylococcus scalded skin syndrome involves widespread desquamation of the upper layers of the epidermis, because the infants in which it occurs can’t excrete toxins through their kidneys, and it can also happen in people with renal impairment as well.
=A
An organ such as the skin can become infected from direct innoculation, exogenously, or it can spread from an underlying structure such as a lymph node or a lung. This is Scrofuloderma which manifests in absesses and sinus tracts. And this looks very similar to a different condition-hidradenitis suppurativa, which is a non-infectious inflammatory condition that generally infects the skin folds such as armpits. Scrofuloderma doesn’t have a particular preference to armpits or skin folds, but it does look very similar in this picture.
B is wrong as cutaneous TB, unlike Herpes Zoster, has many different appearences, and it can be very difficult to recognise what it is, so this is an example where you rely more on diagnostics.
C is wrong as it is a fastidious organism, so you can get flase neg cultures, so there are other ways of diagnosing it
The Ziehl-Neelsen stain (used for detecting acid-fast bacilli) is a good way of identifying the organism, microbacterial PCR can help, and the interferon gamma release assay can also support the diagnosis.
=B
B is the only one that is not a manifestation
Lentigo Maligna is a form of melanoma that usually affects the face. It’s a preinvasive form, it’s a type of melanoma in situ.
Lues Maligna is this ulcerative, necrotic, escharotic form of secondary syphilis, that manifests with these pustules, ulcers, nodules, eschars (dead tissue that sheds or falls off from the skin. It’s commonly seen with pressure ulcer wounds (bedsores). Eschar is typically tan, brown, or black, and may be crusty).
A-condyloma lata are wart-like lesions on the genitals. It’s actually secondary syphilis.
B-Exathem, a rash
C-oral ulcers
This shows how varied secondary syphilis can look. It’s the great mimicker, so it’s one of those conditions where it’s almost always reasonable to check for it with serology.
=Tularaemia-it is caused by the bacterium Francisella tularensis, and it involves a painful lesion that undergoes necrosis forming an ulcer.
Cutaneous anthrax-the ulcer itself is painless but the lympadenopathy is painful.
Syphilis can also manifest with an ulcer and lymphadenopathy, both are painless and similarly primary tuberculosis chancre is also painless.
chancre= a painless ulcer
MRI can facilitate diagnosis, particularly helpful in the early stages where it’s simply dusky erythema and the dramatic necrotising process hasn’t fully become evident as it is in this picture.
It is usually a polymicrobial synergistic infection, but fungi can also cause it.
Fournier’s gangrene is the form of it that affects the male genitalia
C is wrong because necrotising fasciitis develops really over the course of hours and pyoderma gangrenosum isn’t such a strong process. Also with necrotising fasciitis the patient will be unwell with a fever. It is not a therapeutic dilemma, because if you are in any doubt about necrotising fasciitis you’ll initiate antibiotics and debridement. But in pyoderma gangrenosum, you have more time, so it is an easy treatment decision, if in doubt, treat for necrotising fasciitis.
Lyme disease can become complicated, it can involve the nerves, it can cause facial nerve palsy, peripheral nerve issues, it can effect the heart, it can affect our joints. So it is not a good condition to allow develop into its more advanced stages and complications.
Serology is not sufficiently accurate as you have false negs
Taking a biopsy is not going to be helpful as the histiological features are non-specific, so you are relying on a degree of clinical suspicion. The treatment is fairly simple, usually it’s simply doxicyclin for a finite period of time eg 2-3 weeks. So it is reasonable to treat it if your suspicious about it.
Primary lesions are solitary not multiple
Think of leprosy like a continuum. On one end you have lepromatous leprosy, that’s when you have a lot of the organism in your skin, and you have lots of papules and nodules and macules. And it can look really variable, and the sensation in those are normal until very very late on. The differences in the presentations are related to the body’s immune response.
Tuberculoid lesions are solitary and there is hardly any organism, but they tend to be numb. They also don’t sweat or have hair.
It is a spectrum though so you can have dimorphous leprosy, where you have a bit of both, ie features are inbetween. And you also have indeterminate leprosy which is early on where you can’t asign it to either end of the continuum.
Male patient in top pic has thickened skin, so that is a key feature.
Anetoderma isn’t an infection. It is photographed in the top right and it is just a depression in the skin, and that can happen for various different reasons, it can be observed after folliculitis, it can happen in lupus, but it is not an infection.
Erythema migrans refers to cutaneous lyme’s disease.
Scrofuloderma, left bottom pic (remember earlier pic of it in the armpit). Scrofuloderma is a type of cutaneous TB which contiguously spreads from an underlying structure. So this patient has it sprouting from what looks like her perotid gland.
Dermatophytes are superficial fungal infections that feed on keratin in our skin or hair or nails.
Majocchi granuloma is where you have a dermatophyte in the hair follicle that has penetrated the wall going into the dermis, so that is the only dermatophyte infection.
Id reactions can happen in the context of a dermatophte reaction, but the id is short for dermatophyatid. But the id reaction refers to the secondary inflammatory response that the body mounts. It is kind of a hypersensitivity against the dematophyte, so it’s not an actual infection in itself.
Erythrasma does look like tinea corporis, it does look like a dermatophyte infection, but it is caused by bacteria, so it’s a superficial bacterial infection caused by Corynebacterium.
Similarly pitted keratolysis can have that wet look of athletes foot, but it causes pits in the skin and it’s caused by a bacterium.
Purpura fulminans is a form of disseminated intravascular coagulation which can happen in PVL-staph. So you get clotting and bleeding. Some of the other serious complications of PVL-staph can be necrotising pnemonia, remember PVL stands for leukocidin, so it destroys white blood cells, it can also destroy tissue hence necrotising pneumonia and necrotising fasciitis as complications.
Erysipeloid typically caused by handling raw meat or fish
B and C are both non-infectious inflammatory processes
These pics all look very similar, so part of the diagnosis is looking at the history!
Remember Scarlett fever is rapidly spreading, it’s preceeded by sore thorat, headache, fever, chills, and then within 12-48 hours you’ve got a rapidly spreading pink rash with a sandpaper like texture. So scarlett fever is caused by strep, it is the only bacterial one here.
The others are all viral in origin and they have a different evolution, so a slower evolution.
Gianotti-Crosti can be caused by a number of different viruses, including EBV, CMV, even hepatitis B, and it happens in very very young children. And you get on the extremities, the outer surface, and also the face sometimes, this symmetrical papular (ie raised) eruption.
Cryotherapy-liquid nitrogen
Treatment for scabies
The options are topical permethrin. We apply that all over the body for about 10 hours before washing it off, below the neck, including under the finger nails, then we repeat this again about 10 days later. Alternative is oral ivermectin. All household contacts need to be treated as well.
Actinic keratoses=sun damage
Although most of the time the condition does respond to one treatment, it’s the general advise from most sources to repeat the treatment after about 10 days to kill mites and eggs.
Mucomycosis doesn’t respect anatomical boundaries and is an aggressive condition so shouldn’t wait to treat. Also shouldn’t wait for culture as it is only positive in a 3rd of cases anyway. Diabetic ketoacidosis or diabetes is one of the highest risk factors for this.
