View this 30 mins video on the Website.
This Course will be problem orientated using the basic resources of this website and the 6th Edition of Habif's book Clinical Dermatology. It will concentrate on diagnosis and treatment but will also highlight areas in which skin diseases may be confused with skin cancer. This will be particularly helpful for doctors working in Skin Cancer Medicine. Many of the details of specific skin conditions are best presented in book form rather than online. Online teaching websites such as this are better at giving you excellent images, quizzes, teaching cases and other interactive techniques to aid your learning. I will point out what is important and try to direct your reading and online browsing to keep everything relevant.
I will make extensive use of existing online resources such as Dermnet NZ which is particularly suited to GPs and easy to access. At times I will also reference to eMedicine but only in subjects which I feel need greater depth of knowledge or to provide more information on the drugs used in a particular condition.
The teaching concept behind this course is to do a comment on each of the chapters in Habif's book outlining the major points of the conditions discussed, pointing out the areas that a course participant needs to concentrate on to get an all round general knowledge of dermatology and to supplement these comments, where necessary, with an illustrative Teaching Case. Each module will have Images for diagnosis in the Image diagnosis section and also use will be made of Rollovers to highlight clinical features in diagnosis.
Habif's book is better than most general practice textbooks but it is not as detailed as say Bologna's Dermatology which is more suitable for specialist dermatologists. Habif's book though is very well illustrated and beautifully written. It also has some excellent flow diagrams and tables and is a very practical book. It is the ideal book for a general practitioner with an interest in dermatology. It can be ordered in Australia from any major medical bookshop. It is probably cheaper to purchase it via Amazon.
Before tackling this course you might like to review the Undergraduate Dermatology Course in Studentskinconsult. If you registered for this course early enough you would have been given early access to the studentSkinConsult website.You have access to this site using your course username and password. The undergraduate course is quite detailed. I think you will find it gives you a good grounding to tackle the Membership Course. Login HERE first before clicking the studentskinconsult link. www.aidstudentskinconsult.com The student course was designed for undergraduates. It starts with a description of the heros of dermatology and then describes dermatological terminology before looking at the more common skin diseases. You may not have enough time now to work your way through it before starting on these modules from Habif. It will probably take about two - four hours of viewing to do so.
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| This is the 6th edition of Habif's book. Concentrate on the images in each chapter and just read the text and view the links in the course module. |
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| Check out what to concentrate on in Module 1A |
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| Scabetic burrow with the mite as the triangle at the proximal burrow end. |
Chapter 1
Topics Covered
1. Anatomy, Histology Physiology and Basics of Dermatology
2. Skin terminology
3. Diagnostic techniques in Dermatology.
Principles of Diagnosis and Anatomy. You should read Chapter 1 of Habif's book Clinical Dermatology before beginning this module. Concentrate on his descriptions and the images of primary and secondary skin lesions but dont try to learn the lists of diagnoses associated with regional areas. We will gradually acquire these lists during the course. There is quite a bit of material in this first module but we are just trying to introduce you to relevant terminology in dermatology and how to desribe lesions morphologically. Do not try to remember too much as we will be going over the anatomy of the basement membrane etc when we come to the relevant module. Just get a feel for the language of dermatology from this module.
Dermatology Lexicon
View the video below on the diagnosis of Skin Disease
It is important to have an overall picture of the anatomy of the skin. The epidermis is a stratified squamous epithelium varying in thickness from 0.1 mm on the eyelids to 1mm on the palms and soles. It is made up of keratinocytes organised into different layers. The basal layer is composed of stem cells for the overlying keratinocytes. The stratum spinosum above this is made up of keratinocytes held together by proteins called desmosomes made up of different subtypes of a protein called desmoglein. (These proteins are missing or attacked in some blistering diseases). Above this is the thin blue stratum granulosum made up of keratohyaline granules. These contain filligrin, a protein used to form the structure of the overlying stratum corneum. The latter is the main protective barrier layer of the skin.
In structural terms you have an epidermis with a basement membrane. Under this you then have the papillary dermis in which there are small arborising vessels and nerves that end up there. Below this is the reticular dermis where the larger vessels and nerves run. Beneath this is the fat.
Skin anatomy in relation to surgery will be described later because there are obviously some areas of the body where vessels are near the surface and also significant nerves, particularly the facial nerve and the superficial temporal nerve.
The most important structure in the epidermis is the stratum corneum which provides about 90% of the barrier function of the skin. Hence if you have any disease that causes loss of the top layers of the skin, most of the innate protection has gone and various relatively benign irritants will start to irritate significantly and for example, keep a hand dermatitis going, so preservation and maintenance of the stratum corneum is extremely important in preventing irritant hand dermatitis.
It is also very important in relation to the absorption of drugs across the skin. If you tape strip the skin and remove the stratum corneum it makes it much easier for drugs to penetrate, or if you hydrate the stratum corneum you get greater penetration.
Also note another feature of the stratum granulosum. This is the layer from which melanomas are measured when you are measuring the thickness of a melanoma. This is important because the thickness is the most important determinant of the likelihood of metastatic spread.
Other important cells in the epidermis as well as the keratinocytes are Langerhans cells derived from bone marrow which are macrophages enveloping antigens that penetrate the skin surface and taking them to the local lymph nodes where an immune response is instigated. Melanocytes derived from the embryonic neural crest are also seen on the basement membrane in between the basal layer of keratinocytic stem cells. They provide pigment to overlying keratinocytes and also form nests of nevus cells in benign nevi and melanomas. The last rare cell in the epidermis is the Merkel cell. This also is of neural crest origin and plays a part in sensation at nerve endings. However it also is the cell of origin of the most lethal skin malignancy we can get called a Merkel cell carcinoma.
The histo image below shows the purple epidermis with the basket weave stratum corneum at the surface,the basement membrane at the base of this and the papillary dermis protruding into it. The reticular dermis below has a lymphocytic infiltrate scattered through it with some accentuation around the blood vessels. This is the picture you would see in one of the annular erythemas
Appendigeal structures in the dermis are the hair follicles and eccrine or sweat glands. Various benign tumours can arise from them. Check out the detailed anatomy of the pilo sebaceous unit and the eccrine glands. Note that the infundibulum or opening of the hair follicle is contiguous with the overlying epidermis. Hence lentigo maligna and scc in situ of the epidermis extend down hair follicles! Apocrine glands open into hair follicles and are larger than eccrine glands which open onto the skin surface. They are remnants of the sexual scent glands. The dermal nerves and vasculature are related to both the eccrine sweat glands and the hair follicles. Note that the sebaceous gland is regulated by the endocrine system and not by the autonomic nervous system. Most of the detailed anatomy of these layers is described in the relevant disease sections and we will touch on this again later.
We should be aware of the Immunological cells in the skin because they play such a large part in many skin diseases. We have already mentioned the Langerhans cell which is antigen presenting but there are also the T and B lymphocytes, the Mast cell with it's histamine and prostaglandin contents and the Keratinocyte itself which produces local skin antibiotics, cytokines such as Interleukin 1 and express HLA antigens and intercellular adhesion molecules on the cell surface (ICAMs).
Lastly remember these Skin Functions
- Epidermis - Protection from external factors, bacteria and viruses, chemicals, UV light
- Dermis - Protection from shearing forces
- Subcutaneous fat - Shock absorber
- Bood vessels and Sweat glands- Temperature regulation
- Nerve endings - Sensation
- Sebaceous glands - Skin lubrication
- Epidermis [plus UVB) - Vitamin D synthesis
- The image below is the immunofluorescence of bullous pemphigoid. What immunoprecipitants are deposited at the basement membrane in this condition?
The rest of chapter one relates to the description of dermatological lesions and the diagnosis of skin disease. I think it is important to know the primary lesions such as a macule, papule or nodule etc and look at the many examples and lovely photographs Habif gives in this first chapter. However, at this stage I would not concentrate on the various diseases of which there are many examples. I would though look at pustules, vesicles and bullae because the diseases associated with them are relatively specific and well defined. When it comes to actual skin diagnosis I prefer a system that describes rashes as being either red or skin coloured with associated scales or no scales.
This diagnostic algorithm is best shownat my latest blog Differential Diagnosis in Dermatology. There the commonest diseases in each of these categories are outlined and described. The pictures are of the commonest variants. I think you will find it easier to diagnose skin disease if you use this technique rather than one based on whether something is a macular or papular rash. The image below is of erythema annulare centrifugum. It is the A of PETAL in the PMs PET (PETAL) the mnemonic for the red scaly rashes. The histology is shown at Part 2 above
The secondary skin lesions that Habif describes are worth looking at as well, especially the crusts and erosions and even the fissuring section. The special skin lesions such as comedones and milia are also worth looking at and the conditions in which they occur. Comedones are the hallmark of acne but they are commonly seen in the elderly on the face and neck in severely sun damaged skin. Milia formation you expect after skin injury. It is seen in porphyria cutanea tarda when the blisters heal and also with some of the other scarring immune blistering diseases. It can be a problem after dermabrasion but can also occur in some women on the cheeks for no good reason! You need to manually release them.
Investigations in Dermatology Just look first with a good light! Consider doing skin scrapings if a red scaly disease to exclude or confirm a fungal infection. Consider taking a 3mm punch biopsy. Much additional information on a skin disease can be had from a skin biopsy. Consider buying and using a dermatoscope. We will deal with these investigations in the Weekend Meeting. Patch testing is useful in a case of suspected allergic contact dermatitis and using a Wood's lamp (bluelight) can help in showing up areas of pigment loss in vitiligo and determining the depth of pigment deposition in melasma.(It accentuates the pigment if it is in the epidermis)
Microscopic terminology is obviously important to understanding a skin biopsy report. As a reference source you might find the video below of value but it is a bit advanced for you at this stage in the course. Getting Under the Skin- The Pathology and Dermatoscopy Reports Click on the box at the bottom right hand corner of the video to make it full screen. Use ESC on your computer to go back to normal size.
Chapter one also details regional differential diagnosis. I must admit I find this quite useful and you will see it as part of the differential diagnosis technique in the education section of skinconsult. Often if the primary morphology does not help you, the actual location of the rash gives you a series of likely differential diagnoses and as common things occur commonly, it is important to know the common causes of disease in each of these areas. Again this is best outlined at the Differential Diagnosis lists in Globalskinatlas. Try the combination of a specific site and morphology or just use the Site Specific disease analysis area. This does not list every disease that occurs at that site but does indicate some diseases that tend to be found at that site in preference to elsewhere on the body.
I have looked over the images Habif uses to illustrate his approach to Regional Differential Diagnosis. This video gives my comments on these images emphasing the ones which in my opinion can best be diagnosed by finding them in these specific areas.
This is another good reference area in Dermnet on common diagnoses in specific body areas.
Also later on in the course you might find this site of value when trying to work out a diagnosis
Taken from my blog Differential Diagnosis in Dermatology. For more details see DD Derm Blog
1. Diagnosing skin diseases is not difficult. You look at a rash and decide if it is red and scaly or red and non scaly. If it is red and scaly you use the mnemonic PMs PET (PET is Psoriasis, Eczema and Tinea. This is the Prime Minister's Pet ( I used to always think of Kevin Rudd with a siamese cat called Petal sitting on his lap!) The first P of PM is for Pityriasis rosea or Pityriasis versicolor and the M is for Mycosis fungoides, a T cell lymphoma of the skin.) View red scaly rashes Now we know that his pet cat is called PETAL. This helps us to remember Psoriasis, Eczema and Tinea but also the less common red scaly diseases of A for Annular erythemas and L for Lupus erythematosus and Lichen Planus.
So in summary the Prime Minister's pet PMsPET is PET Psoriasis , Eczema, Tinea then Pityriasis rosea, Pityriasis versicolor and Mycosis fungoides. We know his cat is called PETAL so we dont forget the Annular erythemas and Lupus and Lichen planus! And remember Solar!
2. If it is red but not scaly consider Cellulitis, Urticaria, Drug reaction, Viral exanthem or Annular erythema .The mnemonic is C U at the Department of Veterans Affairs Eve (your girlfriend Evie) (CUDVA EVIE) where EVIE stands for Erythema multiforme, Vasculitis and Erythema nodosum. I-Infiltrates of cells or substancesView the red non scaly rashes
3. If there are Pustules then the mnemonic is II
(aye aye) Infective( viral, bacterial, fungal) or Inflammatory eg psoriasis or a pustular drug reaction. Common causes include Staph folliculitis , modified fungal infection or if the vesicles are grouped herpes simplex. Pustules on the face are Acne, Rosacea, Staph folliculitis or H Simplex if grouped. View the pustular rashes
4.
If there are Blisters The mnemonic is ICI(Imperial Chemical Industries) Inflammatory including Immunological, Contact dermatitis and Infective. Inflammatory causes can include drugs but remember Immunological causes in the elderly particularly bullous pemphigoid. Contact dermatitis usually gives smaller vesicles rather than blisters but individual vesicles can join up into blisters. If blisters are linear and itchy it is probably a Plant contact dermatitis. Infective blisters are usually bullous impetigo due to a staph infection. If in a dermatomal distribution blisters are likely to be Herpes Zoster. View the blistering rashes
See examples of these mnemonics in action in Section 10 below.
I appreciate that some of you taking this course are primarily involved in Skin Cancer Medicine. Most of the directly relevant dermatology to your field does not come up until module 10 but I will add a section at the end of each module to illustrate those conditions from that module that you might confuse with a skin cancer. In Australia because of the prevalence of skin cancer and sun damage , it is wise to consider any solitary scaly patch or ulcer as suspicious and biopsy accordingly.
The image below is of a lady with an extensive scc in situ on her lower leg that was treated for years as a dermatitis before the correct diagnosis was made. The well defined scaly edge should also have you thinking about a fungal infection but your scrapings would have been negative.
Create your own user feedback survey Try this anonymous survey of the info in Module 1A
This is just a little resource from Medscape. If you have not yet signed up for Medscape you should do so. It has some useful resources. Click here for some Slide Shows
Below are examples of the mnemonics being used. I appreciate you need to know some dermatology before you can apply them well but the common conditions come up first and often these are correct! These cases will be analysed using the mnemonics previously learned.
Diagnosis boils down to this -
What do I see?
What mnemonic will I use?
What are my likely differential diagnoses?
Where else will I examine or what tests will I do to arrive at the likely diagnosis?
What now is my preferred diagnosis?
Hence what is my treatment?
What do I see? This is obviously a red scaly lesion. Note there are two other smaller lesions near it.
What mnemonic will I use? The PMs PET mnemonic applies.
What are my likely differential diagnoses? Is it psoriasis, eczema or tinea?
Treated psoriasis can heal in the middle leaving a scaly outer edge. It is not broken or weeping on the surface for eczema. It has a peripheral scale for tinea so it could be a fungal infection.
Now what about the PM bit. Pityriasis rosea possible if this was the big herald patch early lesion. Pit rosea often has a trailing scale that points inward. Pit versicolor is less likely with the central clearing.
On balance this could be a tinea( ringworm) infection or the herald patch of pityriasis rosea.
Where else will I examine or what tests will I do to arrive at the likely diagnosis? The history would help but you should do some scrapings of the lesion's scaly edge for fungal microscopy and culture. You might also check the other usual sites for psoriasis.
Examination of this patient elsewhere showed the typical oval lesions following the lines of the ribs seen in pityriasis rosea.
What now is my preferred diagnosis? What we have been examining is the herald patch of Pityriasis Rosea.
Hence what is my treatment? View DermNet for more information on Pit rosea.
Case 2
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