Dermatology Flashcards
What is a macule and a patch?
Macule: circumscribed flat area of colour change ≤ 1 cm diameter
patch: > 1 cm
what is a papule?
discrete elevation < 1cm in diameter
what is a nodule?
like a papule but deeper (into dermis or SC layer) > 1cm in diameter
what is a plaque?
Raised area >1cm diameter with flat top
What is a Vesicle ?
Small (<!cm diameter) fluid filled blister
what is blister/bullae?
Large (>1cm) fluid filled blister
what is a pustule
visible accumulation of pus in a blister
what is petechiae/purpura?
Petechiae - tiny macule due to extravascular blood in dermis
Purpura - larger, may be palpable
what is the general anatomy of the skin?
The outer layer is the epidermis, a stratified squamous epithelium consisting mainly of keratinocytes. The epidermis is attached to, but separated from, the underlying dermis by the basement membrane. The dermis is less cellular and supports blood vessels, nerves and epidermal-derived appendages (hair follicles and sweat glands). Below it is the subcutis, consisting of adipose tissue.
What is the thickness of the epidermis?
In most sites, the epidermis is only 0.1–0.2mm thick, except on the palms or soles, where it can extend to several millimetres.
what is the epidermis made up of?
Keratinocytes make up approximately 90% of epidermal cells
Desmosomes
Langerhan’s cells
Melanocytes
Merkel cells
What are the layers of the epidermis?
Outer: Stratum corner (keratin layer)
then the granular layer
then the prickle cell layer
then the basal cell layer
what is the main proliferative compartment of the epidermis?
The basal layer
What do Keratinocytes synthesise?
Keratinocytes synthesise a range of structural proteins, such as keratins, loricrin and filaggrin (filament aggregating protein), which play key roles in maintaining the skin’s barrier function. Keratinocytes are also responsible for synthesis of vitamin D under the influence of ultraviolet B (UVB) light.
What can mutations in keratin genes result in?
blistering disorders and ichthyosis (characterised by scale without major inflammation).
what is the progression of keratinocytes through the epidermis?
As keratinocytes migrate from the basal layer, they differentiate, producing a variety of protein and lipid products. Keratinocytes undergo apoptosis in the granular layer before losing their nuclei and becoming the flattened corneocytes of the stratum corneum (keratin layer).
What is the function of the Stratum Corneum?
ct as a hydrophobic barrier is the result of its ‘bricks and mortar’ design; dead corneocytes with highly cross-linked protein membranes (‘bricks’) lie within a metabolically active lipid layer synthesised by keratinocytes (‘mortar’). Terminal differentiation of keratinocytes relies on the keratin filaments being aggregated and this is, in part, mediated by filaggrin.
What can mutations in the Filaggrin gene lead to?
Mutations of the filaggrin gene are found in icthyosis vulgaris and in some patients with atopic eczema.
What links the basal keratinocytes ?
desmosomes
What is the function of desmosomes?
to transmit and dissipate stress
disease that affect desmosomes, such as pemphigus, result in blistering due to keratinocyte separation
What is the function of Langerhan’s cells?
they are dendritic , bone marrow-derived cells that circulate between the epidermis and local lymph nodes. Their prime function is antigen presentation to lymphocytes. Other dermal antigen-presenting dendritic cells are also present.
what is the function of melanocytes?
Melanocytes: these occur predominantly in the basal layer and are of neural crest origin. They synthesise the pigment melanin from tyrosine, package it in melanosomes and transfer it to surrounding keratinocytes via their dendritic processes.
What is the function or Merkel cells?
Merkel cells: these occur in the basal layer and are thought to play a role in signal transduction of fine touch. Their embryological derivation is unclear
What is the function of the basement membrane?
an anchor for the epidermis and allows movement of cells and nutrients between dermis and epidermis.
The cell membrane of the epidermal basal cell is attached to the basement membrane via ……………..?
hemi-desmosomes.
What is the lamina Lucida?
The lamina lucida lies immediately below the basal cell membrane and is composed predominantly of laminin.
Anchoring filaments extend through the lamina lucida to attach to the lamina densa
What is the lamina densa?
electron-dense layer consists mostly of type IV collagen; from it extend loops of type VII collagen, forming anchoring fibrils that fasten the basement membrane to the dermis.
What is the dermis?
The dermis is vascular and supports the epidermis structurally and nutritionally. It varies in thickness from just over 1mm on the inner forearm to 4mm on the back.
What is there dermis made up of?
Fibroblasts are the predominant cells but others include mast cells, mononuclear phagocytes, T lymphocytes, dendritic cells, neurons and endothelial cells.
The acellular part of the dermis consists mainly of collagen I and III, elastin and reticulin, synthesised by fibroblasts.
Support is provided by an amorphous ground substance (mostly glycosaminoglycans, hyaluronic acid and dermatan sulphate), whose production and catabolism are altered by hormonal changes and ultraviolet radiation (UVR).
Based on the pattern of collagen fibrils, the superficial dermis is termed the ‘papillary dermis’, and the deeper, coarser part is the ‘reticular dermis’.
What is the cycle of hair growth ?
Human hairs grow in a cycle with three phases: anagen (active hair growth), catagen (transitional phase) and telogen (resting phase). The duration of each phase varies by site. On the scalp, anagen lasts several years, catagen a few days and telogen around 3 months. The length of hair at different sites reflects the differing lengths of anagen.
What are sebaceous glands?
Sebaceous glands are epidermal downgrowths, usually associated with hair follicles and composed of modified keratinocytes. The cells of the sebaceous gland (sebocytes) produce a range of lipids, discharging the contents into the duct around the hair follicle.
What controls sebum excretion?
Sebum excretion is under hormonal control, with androgens increasing it (as do progesterones, to a lesser degree) and oestrogens reducing it.
what is the function of sweat glands?
They play a major role in thermoregulation and, unusually, are innervated by cholinergic fibres of the sympathetic nervous system. Eccrine glands of the palms and soles are innervated differently and are activated in the ‘fight or flight’ response. Apocrine sweat glands are restricted to the axillae and the mammary and genital areas, are connected to hair follicles and are not involved in thermoregulation.
what is an important role of blood vessels in the skin?
thermoregulation
what part of the skin provides protection against chemical, particles desiccation ?
Stratum corneum
what part of the skin provides protection agains UV radiation?
melanin produced by melanocytes and transferred to keratinocytes
Status corneum hyper proliferation
what part of the skin provides protection against antigens, haptens?
Langerhans’ cells, lymphocytes, mononuclear phagocytes, mast cells, dermal dendritic cells
what part of the skin provides protection against microorganisms?
Stratum corneum, Langerhans’ cells, mononuclear phagocytes, mast cells, dermal dendritic cells
What part of the skin prevents loss of water, electrolytes and macromolecules?
stratum corneum
what part of the skin is the shock absorber?
Dermis and SC fat
what part of the skin is responsible for sensation?
specialised nerve ending mediating pain and withdrawal itch leading to scratch and removal of parasite
what part of the skin is responsible for metabolism?
predominantly keratinocytes
Detoxification of xenobiotics, retinoid metabolism, isomerisation of urocanic acid
what part of the skin is involved in temperature regulation?
Eccrine sweat glands and blood vessels
what is a wood’s light?
Wood’s light is a long-wavelength UVA/short-wavelength visible (violet) light source that can be used in various ways.
What are skin biopsies usually stained with?
haematoxylin and eosin
What is patch testing used for?
Patch testing is the investigation of choice for delayed, cell-mediated, type IV hypersensitivity reactions to topical agents, which clinically manifest as dermatitis.
what are prick tests used for?
Prick tests are used to investigate cutaneous type I (immediate) hypersensitivity reactions to various antigens such as pollen, house dust mite or dander. The skin is pricked with commercially available stylets through a dilution of the appropriate antigen solution.
What is photo testing?
Phototesting is extremely valuable in the assessment of suspected photosensitivity. The mainstay investigation is monochromator phototesting, which involves exposing the patient’s back to increasing doses of irradiation using narrow wavebands across the solar spectrum and then assessing responses at each waveband, using the minimal erythema dose (MED) as the endpoint. This is the dose required to cause just perceptible skin reddening (erythema) and is compared with values for the normal population.
What is the definition of crust ?
dried exudate of blood or serous fluid
What is the definition of scale?
a flake arising from the stratum corneum; any condition with a thickened stratum corneum can cause scaling
How to assess for malignant melanoma?
Asymmetry
*Border irregular
*Colour irregular
*Diameter >0.5cm
*Elevation irregular
(+ Loss of skin markings)
what are the major and minor features of melanoma?
*major features: change in size, shape and colour
*minor features: diameter >0.5cm, inflammation, oozing, bleeding, itch or altered sensation.
Atopic eczema
Distribution:
Morphology:
Associated signs:
Distribution: face and flexures
Morphology: poorly defined erythema and scaling, vesicles, lichenification if chronic
Associated signs:
shiny nails
infra-orbital crease
dirty neck (grey-brow discolouration
Psoriasis
Distribution:
Morphology:
Associated signs:
Distribution: extensor surfaces, lower back
Morphology: well defined, erythematous plaques, silvery scale
Associated signs:
nail pitting, onycholysis, scalp involvement, axillae and genital areas often affected, joint involvement, Kobner phenomeom
Pityriasis rosea
Distribution:
Morphology:
Associated signs:
Distribution:
Fir tree pattern on trunk
Morphology:
well defined, small erythematous plaques, collarette of scale
Associated signs:
herald patch
drug eruption
Distribution:
Morphology:
Associated signs:
Distribution:
Widespread
Morphology:
Macules and papules
erythema and scale
exfoliation
Associated signs:
possible mucosal involvement or erythroderma
Lichen plants
Distribution:
Morphology:
Associated signs:
Distribution:
distal limbs, flexural aspects of writs, lower back
Morphology:
shiny, flat topped violaceous papules, Wickham’s striae
Associated signs:
white lacy networks on buccal mucosa
nail changes
scarring alopecia
Kobner phenomenon
why do blisters occur?
Blistering occurs due to loss of cell adhesion within the epidermis or subepidermal region
what is an erosion?
an area of skin denuded by complete or partial loss of the epidermis
Erosions can occur if the there is a split high in the epidermis (below the stratum corneum) as the blister toof is so fragile that it ruptures easily, leaving erosions
When may erosions occur?
pemphigus foliaceus, staphylococcal scalded skin syndrome and bullous impetigo.
when do blisters occur?
When the split is lower in the epidermis, the intact flaccid blisters and erosions may be seen
occurs in pemphigus vulgarise and TEN
when are tense-roofed blisters seen?
when the split is subepidermal - then tense roofed blisters are seen
this occurs in bulls pemphigoid, epidermolysis bulls acquistia and porphyria cutanea trade
what occurs if there is foci of separation at different levels of the epidermis?
If there are foci of separation at different levels of the epidermis, such as may occur in eczema, then multilocular bullae made up of coalescing vesicles can occur.
what may cause localised vesicular blisters?
Herpes simplex
Herpes zoster
Impetigo
Pompholyx
What may cause generalised vesicular blisters?
Eczema herpeticum*
Dermatitis herpetiformis
Acute eczema
What may cause localised bullous blisters?
Impetigo
Cellulitis
Stasis oedema
Acute eczema
Insect bites
Fixed drug eruption
What may cause generalised bullies blisters?
Toxic epidermal necrolysis*
Erythema multiforme
Stevens–Johnson syndrome*
Bullous pemphigoid
Pemphigus*
Epidermolysis bullosa acquisita
Lupus erythematosus
Porphyria cutanea tarda
Pseudoporphyria
Drug eruptions
What is important when taking a history about blisters?
onset
progression
mucosal involvement
drugs
systemic symoptoms
distribution
extent
morphology
what is the Nikolsky sign?
sliding lateral pressure from a finger on normal-looking epidermis can dislodge and detach the epidermis in conditions with intra-epidermal defects, such as pemphigus and toxic epidermal necrolysis.
where are the nerve endings that signal an itch?
In the epidermis of near the derma-epidermal junction.
what are primary and secondary skin changes from and itch?
primary (a process in the skin causing itch) or secondary (skin changes caused by rubbing and scratching because of itch).
what are some examples of secondary causes of pruritius?
liver diseases (mainly cholestatic diseases, such as primary biliary cholangitis), malignancies (generalised itch may be the presenting feature of lymphoma), haematological conditions (generalised itch in chronic iron deficiency or water contact-provoked (aquagenic) intense itch in polycythaemia), endocrine diseases (including hypo- and hyperthyroidism), chronic kidney disease (in which severity of itch is not always clearly associated with plasma creatinine concentration) and psychogenic causes (such as in ‘delusions of infestation’).
What are causes of pruritus in pregnancy?
Polymorphic eruption of pregnancy
acute cholestasis of pregnancy
Pemphigoid gestations
Prurigo gestationis
Pruritic folliculitis
what are the features of polymorphic eruption of pregnancy?
pruritic urticarial papules and plaques
Typically occurs in first pregnancy and uncommonly recurs
Occurs during the third trimester and after delivery
Polymorphic urticated papules and plaques, start in striae
Mange with chlorphenamine, emollients, topical steroids
what are the features of cholestasis in pregnancy and what is the management?
Third trimester and commonly recurs in subsequent pregnancies
Abnormal liver function tests
increased fetal and lateral risk
Treat with:
- emollients
- Colestyramine
- UVB
- early delivery
What are the features and treatment for Pemphigoid gestationis?
Can present at any stage of pregnancy, often occurs in the second trimester and commonly recurs in subsequent pregnancies
Urticated erythema, blistering initially periumbilical
Treat with topical or oral glucocorticoids
what os photosensitivity?
Cutaneous photosensitivity is an abnormal response of the skin to UVR or visible radiation.
abnormal photosensitivity occurs when a patient reacts to lower doses than would normally cause a response, either with a heightened erythemal reaction or the development of a rash.
What is Photo-aggravated skin diseases?
Photo-aggravated skin diseases are exacerbated by sunlight but not caused by it.
What are immunological causes of photosensitivity/photo-aggravated diseases?
Polymorphic light eruption
Chronic actinic dermatitis
solar urticaria
Actinic prurigo
Hydroa vacciniforme
What are the drugs causes of photosensitivity/photo-aggravated diseases?
Photoxicity - usually UVA photosensitivity
Pseudoporphyria - NSAIDs, retinoids, tetracyclines, furosemide,
Photallergy - usually to topical agents, particularly sunscreens and NSAIDs
what are metabolic uses of photosensitivity/photo-aggravated diseases?
Porphyrias (mainly porphyria cutaneous trade and erythropoietic protoporphyria)
Pellagra
What diseases may you get photo-aggravation of ?
Lupus erythematosus
Erythema multiforme
Rosacea
Investigations for photosensitivity?
monochromator phototesting
Provocation
Patch or photo patch testing
screen for lupus and porphyrias
HLA typing in suspected actinic prurigo
DNA excision repair functional activity or genotyping in suspected xeroderma pigmentosum
How is photosensitivity and photo-aggravated diseases managed?
Management depends on the cause
If photo toxic drug or chemical this must be identified and addressed
Council in regard to sun avoidance is essential
Phototherapy - can be used to induce hardening which is a term used to describe the process by which phototherapy cross-links structures in the skin
Antihistamines - useful in solar urticaria
Systemic immunosuppression - sometimes required in the immunological photodermatoses such as chronic actinic dermatitis
Patients will often require vitamin D supplements
what are the causes of leg ulcers?
Venous hypertension
Arterial disease
Small vessel disease
Haematological disorders
Neuropathy
Tumour
Trauma
what are pre-disposing factors venous leg ulceration?
Varicose veins
DVT
Obesity
How do venous leg ulcers present?
The first symptom in venous ulceration is often heaviness of the legs, followed by oedema. Haemosiderin pigmentation, pallor and firmness of surrounding skin, and sometimes venous/gravitational eczema subsequently develop. This progresses to lipodermatosclerosis – firm induration due to fibrosis of the dermis and subcutis, which may produce the well-known ‘inverted champagne bottle’ appearance. Ulceration, often precipitated by trauma or infection, follows. Venous ulcers typically occur on the medial lower leg
How do arterial leg ulcers present?
What are the risk factors
Deep, painful, punched-out ulcers on the lower leg, especially the shin and foot and in the context of intermittent claudication, are likely to be due to arterial disease. Risk factors include smoking, hypertension, diabetes and hyperlipidaemia. The foot is cold and dusky, and the skin atrophic and hairless. Peripheral pulses are absent or reduced. In these circumstances a vascular surgical assessment should be sought urgently.
How are leg ulcers managed?
Lifestyle - exercise, weight loss and smoking cessation
If there is oedema - elevate legs
If no arterial compromise - compression bandaging from toes to knees to enhance venous return (ABPI should be > 0.8)
If ulcer is purulent - week potassium permanganate soaks may help
Systemic antibiotics are indicated if there is evidence of infection
Various techniques of split-thickness grafting (such as pinch and mince grafts) may hasten healing of clean ulcers but do not reduce recurrence risk.
What conditions may present with or progress to erythroderma?
Eczema, psoriasis, drug eruptions and cutaneous T-cell lymphoma (Sézary syndrome) are among the diseases that can either present with, or progress to, erythroderma.
Other causes include the psoriasis-like condition pityriasis rubra pilaris, and rare types of ichthyosis.
How may patients with Erythroderma present?
Erythrodermic patients are usually systemically unwell with shivering and hypothermia, secondary to excess heat loss.
However, they may also be pyrexial and unable to lose heat due to damage to sweat gland function and sweat duct occlusion.
Tachycardia and hypotension may be present because of volume depletion.
Peripheral oedema is common in erythroderma, owing to low albumin and high-output cardiac failure.
Lymph nodes may be enlarged, either as a reaction to skin inflammation or, rarely, due to lymphomatous infiltration.
How Is erythrodema investigated and managed?
Investigations to establish underlying cause
skin biopsy may be required.
Supportive measures - adequate hydration, maintenance of core temperature and adequate nutrition.
Insensible fluid loss can be many litres above normal losses. Protein may be lost directly from the skin and through the gut because of the protein-losing enteropathy that often accompanies conditions such as erythrodermic psoriasis.
